I've been using the Wingman FF for a year now. I liked it so much that after two weeks I bought a second one to use for multiplayer, and that was a good idea because now even my aunt & uncle could just sit behind it and start driving - ok so they weren't quite used to this kind of powersteering yet
- but it really resembles a car a lot more and most 'normal' people would've been totally helpless with a DS2.
The Wingman FF is the PC equivalent of the official GT Force wheel and is still available - Amazon even sells it - and it's the best wheel you can buy for $50. It's also the wheel the guys at PD have been using as a benchmark for this game and the FF engine has been tuned to this wheel, which you can tell (esp. if you drive with steering assist on simulation).
It's fine if people do well with the Driving Force, but that's the only wheel on which problems have been reported. The MoMo is also a great wheel as far as I can tell (I see people driving it all the time), though a little impractical. Be careful though to get the right one (i.e. with the USB port, not the Game Port which is PC only).
Lastly, don't believe a word from people like Mr.P who are ace-drivers with the DS2 and then expect to be even better with the wheel instantly. It takes most ace drivers months to get just as good as the DS2, and even then on some track/car combos the DS2 holds an advantage over the wheel. The reason is quite simple - with the DS2 it don't matter how unrealistic, you can always turn the car with a flick of the thumb. With the wheel on Force Feedback you physically cannot do this as fast, ever. That means there are you need different timing. The better you know a track with DS2, the worse this is, because you've learnt a certain timing and so with the wheel in the beginning you're always up to a tenth or two late. In rare cases you simply cannot drive in the same way as the DS2 allows you.
On the other hand, the wheel allows you to drive the realistic lines on a track much easier. With slower cars you will see your times improve fast and the 'realistic' line you will also notice improvements in the tire-wear department.
The more realistic GT gets (or you allow it to be - try Simulation Tires with Simulation steering assist) the more it will favor the wheel. Although there will always be people who will be ace with the analog controls of the DS1/2 as that allows you almost the same amount of control - just slightly harder to pull off and requires really well trained thumbs.
Well, just my 0.02$.
