I just upgraded from the X3 Live, to the HD500.
One thing that always bugged me about the X3 works much better with the HD500:
If your modeling knob is not engaged, and you pull up a patch which forces a model, it WILL TURN IT ON.
This never happened with the X3L.
Sometimes I would start out with songs on magnetic pickups and at some point in the set switch to a patch for an acoustic sound.
If my modeling knob was engaged the patches which specified the MAGS channel would not let the modeling come through, and switching to a patch that forced models would allow only the modeled sounds to come through without the mags... just as you would expect.
The problem was, if I ever forgot to push that knob in and engage the modeling function, when I switch to a patch for a model (typically acoustic), you would still only hear the magnetic pickups. I tried to remember, always, when plugging in my VDI cable immediately engage the modeling function or else I would forget.
This is NOT the case with the HD500! If you push the modeling switch to turn it off (unlit), then select a patch which forces models, you will see the light come back on!!!!
Sorry about the rant, but this excited me last night when I realized it!