Was one of the original backers during development - the game is much, much better with a wheel. I never got the hang of it with a controller.
Pretty good sticky for the controller on the forums here:
http://forum.projectcarsgame.com/sho...guration-Guide
These files are pretty critical if you do end up with a wheel:
http://forum.projectcarsgame.com/sho...-Tweaker-Files
Enjoy! Game's a bit buggy and annoying sometimes, but there is a fantastic racing simulator in there when it works.