I think it's actually getting about time for a POD HD MKii.  Something with more processing power, even the possibility of dual processors for spillover and smooth patch transitions.  I'd even love to see the dedicated boost button, from the POD HD 400, come to the 500.  The POD HD is now two years old, so maybe the next model is well into development.

Oh yeah, something on the "CPU limit exceeded" stuff on the POD HD500.  I wish I could load whatever effects I wanted into each block.  Then, while using the patch, if an effect was going to put it over, just not let me engage it.

..Oh, another thing!   I wish that, like on the M13, you could do different settings for each effect in a block.  Then, you could cycle through them somehow using the assigned footswitch.  That way, I could have three different setups for my delay effect without having to take up three effects blocks, which I can't do anyways because it puts me over the CPU limit.

All these requests sound great. I wish these would've came with 2 independent inputs for allowing 2 guitars to jam

simultaneously. I will "NEVER" venture away from Line6, but a buddy of mine purchased a BOSS JS-10, and i must

say, this thing is the S_ _t !!!  Never been a huge BOSS fan ! But this unit is equipped with that option and it is really

fun... On a different note, I'd love to see the amp models mentioned above + Roland JC120 would be awesome...

1-Real world EQ.

2-Add a spkear cabinet module  indepenent of the amp or preamp, so you can run one amp or preamp into two different speaker cabinets

3-Add option for Power amp alone so you can mix and match power amps with various preamps.

4-Compressor inside the amp module like originally started with Kemper then adopted by AXE II, it's a brilliant idea that Kemper came up with wich makes the dynamic response to the fingers more sensitive than real world amps, You will have the same volume level but if you play hard you distort and play soft and it's clean.

+1 Jazz Chorus Clean

And now for something completely different:

I would like there to be decibel meter as an effects option (like a pre/post fader meter on a board). This wouldn't be something you would use all the time, but it would allow you to insert it as an effect and balance all your patch output levels from within the HD500; versus the way I do it now using a DAW / Mixing board / HD500. Even better make it a global utility that you can use across all patches.

I find using the meters gives a much better base line versus what your ears percieve as loud or soft etc...

Operation:

I want Amp models to represent the amps in a way that amps work. I would like them to model an amp completely not just one part. If I select a Mesa Boogie dual rec I want to that the ability to play with all 3 the channels. I want access to each of the v3 voicings for each channel. Access to the reverb on the amp. etc etc. Dont break the amp into parts and call it 3 new models. This isnt a pissing contest. I want line 6 to model the amps right down to the way the knobs respond for that amp as close as they can get. I own a Dual Rec and anyone else who has one knows they dial in much different then most amps. If I dial my pod in like my Mesa it isnt even close.

They brag about how close the amp sims are too the real deal on one channel but they have left out the other 90% of the amps functions and features.

Cabs:

- Load your own cab/impulses: Its no secret that the cab emulations for the Pod aren't great and many home studio users are getting better results, and making their impulses available to the public. For some reason Line 6 thinks this is terrible and will not allow its users to take advantage of better cab options. Instead they released this Cab DEP thing, which is a cool idea and more flexibility is always welcome but I cant help but think it feels like a bandaid solution that has come out of their stubborness to admit they havent done a good job with cabs. Let us use whatever cabs we want!

-MICS! Add the ability to have multiple mics on one cab and multiple cabs for one cab.

-Mic ROBOT! Add the ability to position Mics around your cabs however you want too. Like  the mic robot Ramsteins guitarist uses in studio.

In Studio / Live:

- Re-amping (duh)!

- Real Eq's, once again Line 6's stubborness to fix this issue baffles me. No I dont want to learn to convert your %'s into Frequencys just so I can make minor tweaks to my amp. NO ONE DOES THIS, BECAUSE ITS A BAD IDEA!

- Speaker Breakup - Add this feature to emulate the way a real amp responds when is it pushed hard at high and low gain situations.

- Overdrive/ Distortion pedals mulligan: Re work the models for these, They are terrible. I actually went out and bought a Ibanez TS9 Overdrive pedal because of how bad the model is for it and others.

Construction:

- On/Off switch: Holy #$% words cannot describe how stupid this move was!

- Longer Power Chord(sic): This is almost as stupid as the on/off switch. It is impossible to play this thing live with a 6'  cord. The X3 Live had a cord that was around 20' long, Hint: Line 6 you had it right the first time.

- Bigger LCD: And use some colors! Even if it is just 8-16 colors, it would make a world of difference in the way you manage all the stuff going on when no computer is handy.

- Bring back X3 Live Handles: It seems kinda wierd but I really miss those! They were big and awesome. Kept you from damaging your unit live with your foot, and I used to carry my X3 Live around everywhere with it. Transporting the HD is just akward, I had to find an old duffle bag to put it in when going anywhere. Yuck!

- Rework the USB Port: For whatever reason it sucks on the HD, there is tons of threads about it breaking on users without any abuse or damage. This includes myself, I had to glue the center piece back in and now Im afraid to even plug it in unless there is new Firmware available that I must have. This should be covered un warrentee as a defect like the audio drop out issues with the X3 Live.

Thats it!

The NR 1 BIGGEST UPGRADE Line 6 could ever do to the pod HD series is to implement custom IR import.

It's baffling that they haven't done this for years! It would kill the competitors for sure in that price range.

The cabs/mics in all the pods have always been the weak point and they make at least 80-90% of the sound.

Anyone who try IR from Redwirez or Ownhammer or create their own eq matched IR's with Ozone know that it's all about IR's.

It's easy to copy perfect guitar tones from recorded tracks or your own amp by creating eq tone matched IR's using Ozone in a DAW.

Custom IR's makes the pod HD sound soooo much better.

On top of what others have said here, I'd like the amp models to be improves as well.  As one poster said, the models could react more like the real deal.  One thing I'd like to HEAR improved on the models is how the modeling represents the highs (especially on the high gain models).  When I listen closely to the HD modeling, I notice that the highs sound like there's some sort of overbearing white noise generator being used, and it makes the highs sound cloudy, indistinct, and a bit unmusical (don't get me wrong; properly tweaked, the models are more than useable/passable in a mix).  When compared to the real thing or a higher end unit like the Axe Fx II, I hear highs that give more of the proper "****** off hornet" type of tone, instead of sounding like some random hissing in the background.  A good example can be found here comparing HD modeling to Axe Fx II modeling.  Listen carefully to the highs on each and see if you notice what I am hearing.

http://www.youtube.com/watch?v=m4AQvDOGuqI

The ONLY thing I want is a realistic EQ. 

I ended up buying a Dual 31 Band EQ to stick between the PODHD and Amp.  I know that was overkill but it made a huge differance.  I tried using the built in EQs, wow that sucked and I think I'm being kind.  They work if you want to spend endless hours figuring them out and wasting multiple slots in the chain.  I feel sorry for the guy that developed them.  He can't have much self-esteem now.  I don't know of anyone that likes them, just a few people that spent enough time to get them to work halfway good.

Line6 created a very good product and I'm happy they did.  For me it would be a great product if it had a realistic EQ.  Did I mention EQs ??????????

The main thing I would like, which I don't think has been mentioned yet, is the ability to save my own default settings for the various amps, effects, etc. It's all well and good having 'template' patches, but once you've got a favourite setting for umpteen amps and effects, the number of combinations makes it totally impractical.

Other than that, I agree with everyone who has mentioned improved EQ, separate pre- and power amps for mixing and matching, the one amp into two cabs thing, and custom IRs would be cool, too.

Some other comments on HD500 firmware (and editor):

GUI: Allow the user to move the expression pedal while setting limit ranges in control function to preview the sound.  Example, setting Drive and Volume to EXP to keep a near constant output with varied drive and volume, moving the pedal takes the GUI out of setting mode.  Need to keep going back and selecting the parameter and min/max values.

Looper:  Add a way to save the default looper settings (pre/post, 1/2 or full speed, etc.).  Global or per patch

Tempo:  Allow a default setting to be saved with each patch. (example, I have a 'surf' patch and it needs a 140bpm tempo but uses the last user 'stomped' value)

Input A/B source:  Add a 'none' setting to the input (so users don't have to select MIC and turn the input gain down).  This would be less ambiguous.

I think IrishPriest's suggestions most closely match my own wishes, but with one exception. So (with some degree of repetiion of Irish's points) I would specifically like :-

Absolute number 1. At least ONE more bass amp model. Something punchy and modern please.

2. Improved and correctly setup (i.e. frequency based) EQ.

3. Improved user manual to explicitly explain the intended usage of basic settings (such as, but not limited to, input settings).

4. (Although it may be my old PC... I see enough comments to suggest) more stability when used with Edit software.

5. (possibly somewhat fantastical) some form of "gain wizard" that when engaged would automatically adjust all gain related parameters in a patch to some pre-determined level, with the ultimate result that all patches have a uniform output. (I realise this would have tonal influences throughout a patch, especially if more than channel and master volumes need to be amended, but I really really wish I could load up new patches (as well as try existing ones I have not yet tried) without the massive differences in level.

6. And as also mentioned before, I would prefer that the modelling was on a more like for like basis i.e. reflecting the specific contols of the unit (most specifically the amp) being modelled.

Other than that, if we were talking about a new peice of HD hardware, then in addition to the above I would like to see:-

1. More robust hardware (I break out into a sweat if I have unplug the USB cable given the reports here... and the epression pedal toeswitch 'crunch / click' is massive detterent from actually using it).

2. DSP DSP DSP... Certainly enough DSP to run existing number of slots but with NO unaobtainable combination.. (I would accept that this would mean there would be spare DSP in probably 95% of patches, and as such some could argue that these could be used for additional blocks... Its a personal thing, but I would just rather know I am not going to run out of puff whatever I use.

3. Wet / Dry out options on analogue and USB.

4. Seperate headphone volume contol.

5. Continuoulsy variable pots (or whatever the correct term is) i.e. ones with an LED ring based indication as to current setting, and therefore are correctly set for each patch selcted.

Having said all this, I am actually pretty happy with the HD as is, and even if all the above were presented in a new model, I'd probably stick with what I have for quite some time to come...... (though that is more my wallet talking than a lack of desire for the listed improvements).