Pros
The health benefits are great. Being able to shut the door and concentrate on what you're working on is a big plus for many. The atmosphere among QA/Devs in the MSTV group was always professional. I had several different managers over the course of the 5 years I was there and I felt they were helpful in career advice / planning and gave honest reviews. Excellent internal discussion lists allow you to chime in and discuss products / issues across the company.
Cons
Company felt like it had too many layers of managers. People outside the company can be snide when they discover your employer is microsoft; I had more than a dozen incidents here in Silicon Valley where people got verbally hostile once they found out where I worked. Traffic on the main highway outside the SV Campus is a nightmare at rush hour. You'll eventually feel like you're camped out inside microsoft while your buddies on the outside are having fun making heroic stuff happen at startups.