I hate to start an argument, but i'm not impressed by the Xbox 360 controller. It's a good controller, but i don't find it any better than any other one out there. It's a good deal more expensive than many as well.
I use the Logitech Dual Action gamepad. Comes in some other varieties such as cordless and rumble as well. I have the original standard one. Replicates the PS1/PS2/PS3 controllers roughly, it has all their buttons (even the R3 clicky analog sticks). Very comfortable and sturdy. It's quite cheap too, you can find it for around $20 most places. It's perfect for everything i use.
There are a few games that don't work without a real 360 controller (Eidos does this for some dick reason). You can just get an xbox 360 controller emulator though and put some dll files in the game directory. It will force even stubborn PC games like mini ninjas to work with your gamepad.
As for games that don't have native gamepad support, use xpadder. You can create custom profiles for games to map keystrokes and even mouse gestures to gamepad buttons or analog. I have one game that won't work with gamepads- Beyond Good and Evil. Managed to use xpadder to map all functions to my gamepad, works great! It is correct that if a game doesn't support analog, it will treat everything as digital. However, it can still feel better than using the keyboard regardless.
