I just picked up the Band Hero kit for cheap (4 guitars and 2 drums, yay!) so I'll check out the new guitar... but yeah, both the GH2 and GH3 guitars killed my hands when I play harder songs. That said, I do have a death grip when trying to move to different frets, so that probably exacerbates the problem... but after a few songs, my hands will start to kill me.
Of course the other thing is that wireless instruments are just a pain because it feels like a waste of batteries. But that's a minor problem in the grand scheme of things I suppose.