If you have not used IR's at all, load up your favorite patches from your POD turn the cabs off, run them through LeCab with some of the free God's Cab impulses. I guaran-f'in-tee it sounds a hundred times better. The longer cab IR's nearly eliminate any left over "fizz" from the preamp that the stock cabs don't cut, the lows and highs are even more "guitar" like, and some of them even included a little tube power amp response....There is no comparison between whats on the POD and what longer, higher resolution IRs can do.....
I see it was something that people who know about, are adamant about, and everyone else is unfamiliar. If they started using something akin to Fractal's Hi-Res IRs in the next POD generation people who didn't even know they wanted it would be applauding the differences.
I say this same thing every time I read a similar thread: to my ears disabling the POD cab doesn't just disable an IR, it sounds like there are other things that get lost. Replacing with another IR never sounded right to me. Unless line 6 officially says that they support external IRs and indicate that disabling the cab can be replaced by another IR, I won't consider using it even in software. Line 6 Cab doesn't tell you whether the IR mic is off axis, on axis, etc; so line 6 cab can be a combination of several IRs as far as I know. No one from line 6 chimed in and said anything about the topic.
If line 6 opens up their cabinet at the software level and give the option of replacing just the IR and not the whole cabinet, I would consider. On the other hand, I also use Eleven Rack and the cabs are called off Axis and on Axis so when I replace those with IR using software VST etc, I get amazing varieties and results but one it comes to POD HD, Line 6 cabs always sound superior to IRs because , I believe, they're not just an IR. I'm personally not complaining as, I personally think I have enough with the Line 6 cabs and don't want to bother spending countless hours auditioning other IRs, but if they ever officially support the IR thing, I would be all over it and would spend the hours to find the best possible IRs.
It's really puzzling to me why they never supported external IRs yet, as it would extend the power and useablity of the PODs and take them to a new level as you are certain to stumble on the perfect speaker simulation (IR) that would suite your guitar,pickups/body, neck etc better than the internal IR that's in the LINE 6 Cabinets (not because it's better, just because it would suite the specific guitar better)