I started with an Xbox 360 pad, but I soon realized that no matter how much tinkering I did, there was no way I could smoothly circle strafe enemies and shoot them with the pad. I can move, I can toggle strafe, but there's no such thing as "aim direction." the simple solution here is to allow you to choose an analog stick to aim in any direction. I'd use the right analog stick on my pad to aim, ala Geometry Wars. I can use the right trigger or right bumper to attack.
Currently, mouse/keyboard is superior for control, but I don't think it's because it just is, it's because proper gamepad support has not been implemented. I prefer using the gamepad for game like this; it's more relaxed and comfortable. This is just preference of course, but the point is that there should be no technical reason why we can't aim properly with a gamepad. Lord Vanaduke is laughing at the gamepad's inability to circle strafe properly.
Correct me if there's already a way to aim fully on the gamepad natively while strafing.
You can set up one analog stick for movement and the other for facing/aiming. I'm not sure exactly how, because I don't have a game pad, but I've seen others play that way (on a Logitech gamepad that looked more like a PS3 controller). One person I play with is particularly fond of running down empty hallways while spinning just because she can.