The ergonomics are rather bulky, but once you've gotten used to it, the triggers and analog sticks are quite good. I'd say 7.5 or 8/10 overall.
What other gamepad has 14 buttons, 6 axes (+1 that LFS doesn't recognize), including nice springy triggers like the xbox's?
The latter emulate the sense of pedals pretty well.
The drivers have never given me any hint of lag or bugs, over about 4 different PC configurations and probably a dozen windows installs.
What other gamepad can do accurate, separate throttle, brake, and steering axes, as well as a second center-returning joystick to use for freeview?
The XBox controllers certainly aren't perfect, but they do the job quite well.