Pros: Benefits, food, work-life balance, environment, endless challenges
Cons: The interview process
Microsoft is a place that can be hard to get into, but once you're in, the opportunities are endless.
When I first started at MS, I was working for another company (Aquantive/Atlas) that was acquired by MS, and the initial transition was hectic, but after a short period of getting to know new management and some new "best practices" things resumed at their normal, yet hectic pace. After a couple years of hard work, a couple promotions and always looking ahead, it became clear that this was the place that I was meant to be.
After some internal struggles with management across MS, we got a new CEO, changed the way we look at the future and eliminated "stack ranking". I now believe that MS is one of the best possible places to work, with endless possibilities for training, development and career advancement.
Yes, it's hard to get in (the interviews are brutal), but if you know your stuff, have a passion to drive the future and like working with other like-minded individuals, don't hesitate, apply for something!