Well, it's challenging, but I've seen a lot of the expert charts, and it wasn't as bad as I thought it would be, after hearing what he said. I'd probably have a lot of trouble on pretty much all the expert charts, but that just means that if they made the hard charts much better than GH2's, I'll have hard and expert to work with.
Making the game harder helps everyone because as long as you keep some easy songs, new players can learn, and for everyone else, there's a lot more room for improvement.
Try playing expert on GH1 and then switch to GH2, you'll nearly shit yourself at the difference in difficulty. I guess the some goes with GH2 to GH3. Oh, and DDR did the same thing when it came out, lol.