Vantaggi
I found Microsoft to be a safe, supportive place to work. Everyone knows their job and sticks to it. People shouldn't take this for granted because in other places, sometimes even your job description and/or expectations is ambiguous. The benefits are great especially free health care. I always felt like my managers and peers had my best interest and my career advancement in mind right up alongside the team's success. I believe that MS is a company of integrity, one that support great causes and supports the employee as far as possible. There is always someone to learn from or some piece of technology to learn about right there in house. So learning and mentorship opportunities are both plentiful.
Svantaggi
You can gain quite a bit of weight from the free drinks, affordable lunches, and frequent summer morale get togethers so while all of the above is good, you need to take advantage of your ProClub pass. The only other downside, I can think of, and I am really struggling, is that you can easily get so comfortable at Microsoft that you never ever leave. I have felt like this and spoken with others who have to force themselves to see other career options/moves. It's hard to give up Microsoft's benefits and stable work environment but having a diverse resume is also very important.