Have 3 and nothing worng with them. One of them has a battery cover that the battery is a very tight fit and hard to get out, otherwise no problems.
My main 360 controller get's dropped almost everyday on wood flooring. Still works great.
My buddy bought one from Sam's club however and the face buttons are sticking right out the package. Not sticky as if soda was poured on it but when the buttons are pressed it takes much longer to depress. Surprisingly, they've gone through more controllers than me. They also got a controller where the RB is loose.