I own the GT3 wheel. After reading the reviews, I decided to blow $100 to get it. Even though I am almost embarased to admit that I dropped that much on a controller, it is very cool. Off the line, you can hold the tach right where you want. Into the turns you can feather the brake and gas simultaneously. The feedback is very good, although not strong enough to rip the wheel out of your hands has you het a curb at 160mph.
They are kind of hard to find. Rather than stalking the stores that carry them, I ordered it off bestbuy.com and it was on the way within a couple of days.
Unfortunately, I still suck pretty bad, but it is a ton of fun. The question you have to ask is, does it make the game three times as good. I would say not that much, but the game is so good that incremental enhancements are worth it.