Pros
My experience with AMD was that on the whole it is a very work life balance oriented company. I always felt the company was a key player in the industry and was moving things forward and challenging conventional thinking in its fight agianst Intel from technological and also "anti-monopolistic" standpoint. This is something to be proud of.
Cons
It might seem too easy to say this but it's true -- the best reason is also the biggest downside to working at AMD. The endlessly repeating cycle between survival and 'almost' abundance that characterizes this company's ongoing battle against Intel. It takes a unique kind of stamina to choose to fight such a battle. The repeated swatting this company takes from Intel gets tiresome after a certain amount of time... although one might say the folks there are gluttons for this kind of punishment, myself included.