Hi,
I am using the XBox 360 controller, with a MS USB crossfire wireless gaming receiver. I find it works very well if you don't have a compatible controller, and is more cost effective than some conversion kits if you have an Xbox 360 (PC interface is about £14/$28 - controllers are about £30 new though).
Also being wireless, you can move about with it, if required.
Just use the Joystick option to set it up. The control options I am using (in order) are:
1,4,5,2,1,4,5,2
Both of the sticks are on a spring on the 360 controller, but this does not seem to be a problem.
I am very pleased with the simulator and hope it continues to improve.