I just got back from the Day o' Shopping. After walking into a Circuit City and finding a Wii version of Guitar Hero III, I got permission from the wife to pick it up and try out.
I can confirm the Wii version is better than the PS3 version - the guitar is working perfectly, star power works like it should, it is *very* responsive, and I think the keys actually feel better.
Funny that one console version of the hardware should feel so much better, but there you have it. Once I find a box big enough, I'll fill out the paperwork and return the PS3 version back to Amazon come Tuesday. Too bad.
I'm going to go cancel my Rock Band purchase as well and hope they come out with a Wii version soon.