Pros
I like that I am surrounded by some of the sharpest brains I have come across. I get stuck? Just walk into my neigbor's office and he'll brainstorm with me. Anytime. Doesn't matter he is 5 levels senior to me. I like that we are agile and anyone from the grass-roots to senior manangement influences what we do. I like that Microsoft will bend the rules to ensure I'm happy. Best of all, I like our software diversity. Get bored with my current job? Heck, I can join any of the 1000 teams here waiting to grab me. Tomorrow.
Kontras
The software diversity of Microsoft is a boon as well a curse, depending on how it influences you. With the 1000+ teams comes a 100 different cultures and working styles. Some are more process-oriented due to the sheer magnitude of the project, some are like College environments - get it done by the deadline, doesn't matter how you do it. There's no way a company of this size can have something called a "working culture". As a newcomer, you might not like the culture of the team you join. However, on the upside, you have 100 different working cultures to choose from too! Oh, and yeah, there's no free lunch! Yet.