I have a datel H2 wireless controller that I got on best buy ( it was on sale for 24.99 plus i had a 10% coupon), and I'm very impressed with it, very good wirless signal and works like the original xbox controller.
If you wanna get a wireless controller get it from a Best Buy, Circuit City, or another store instead of online so its easy to return if you dont like it. Also, get one that looks exactly like the Microsoft controller, the ones with modified design, like the mad catz, are usually crappy (logitech is the exception).