Played it a bit, and just now moved on to GT5. I'd been using the DFGT previously. Honestly, I'm most disappointed with the GT5 feedback. I have finally experienced the "dead zone" I'd heard about. F1 2010 seemed fine to me, but I didn't play it with the previous non-patch FFB either.
Right now the hardest thing is adjusting to the brake pedal. After playing with the DFGT pedals for so long it's quite a drastic change. I've had to switch to left-foot braking now, which may be faster for me in the end, but at the moment I'm having to take time to adjust.
Oh, and it's interesting to come from engine braking so much in the F1 cars to trying to do that on GT5... doesn't work!