Pros
Microsoft's size and product diversity can provide a lot of latitude for a variety of different career experiences. When starting, you'll be expected to stay in-role for at least a year, but after that (depending on the group) you can explore elsewhere within the company. I believe this is the best way to get the most out of the "Microsoft experience". In Microsoft, moving around is good, for a number of reasons. Note that team culture within MS differs widely. Clarify your career goals well, within your own mind, then work hard to get there - leveraging the existing HR processes. As an FTE, the benefits package is the best you'll find. The people at Microsoft, in general, are great. Overall, they are quite smart, and famously passive-aggressive. Don't be intimidated, but also don't over-assert yourself - just be relaxed, knowledgeable, open, vocal and confident. Make a point of getting to know a lot of people.
Cons
Microsoft culture is not as pragmatic as it used to be, and is becoming less so every day. MS people used to want to "change the world" (which they did), but now it's much more about "playing the game". The creeping bureaucracy is not, as some say, the inevitable result of growth - but rather the result of a loss of cultural momentum. As the old-timers leave, and new people join, the culture is shifting - slowly, but inexorably (like global warming). In years passed, it used to be okay to openly challenge virtually anyone's rationale, as long as your argument was strong. Now, that could be politically unwise, and could hurt your career. Bad news used to "travel fast", but now it is more often suppressed. The true impact of modest reportable achievements tend to be exaggerated, often to a great extent. A project with minimal value but great visibility can do a lot to help your career, but the reverse will generally not. Regardless of recent HR attempts to improve team collaboration, the element of intra-team competition remains as strong as ever, even within the formal reward structure. Helping others on your team will usually not impact your review, but "game playing" to improve your visibility at the expense of your peers is usually rewarded. This is true at every level of the company. Microsoft is not unique in this regard - but you should be clearly aware.