Pros
You will be working with smart, engaged co-workers in an almost infinite number of tech fields. For recent college graduates Microsoft can be a wonderful extension to your education - on the job training as long as you stay no longer than five years. I would not recommend working at Microsoft to senior employees, your prior experience will not be valued. You will have access to all the tools you need to be successful in your job. The key to success at Microsoft is picking the right manager and staying with them, which unfortunately, to a great extent, is out of the employee's control.
Cons
As many others have stated, and numerous articles have confirmed, the stack ranking system at Microsoft is stifling innovation. At Microsoft the competition is not firms like Apple and Google, but the peer in the office next door. It is an open secret that Microsoft ages out.