Vantaggi
There are a lot of great opportunities at Microsoft, and room for advancement as well. Additionally, since Microsoft has a diverse set of products, there is the potential for lateral movement if you are interested in exploring a different product area. In addition, you get to use geeky lexicon like "ping me later" or "let's take this offine", etc. :-) Of course, there are the great health benefits...among the best in the biz. This is a great place for someone fresh out of college to work, because there are so many different areas of Microsoft. If Microsoft opens up a substantial presence in the downtown Seattle area in the coming years, I will definitely check out what opportunites there are.
Svantaggi
For me, the biggest problem was the commute. After 10 years or so, it really took it's toll. I like living in Seattle, so whether I drove or took the bus, I could count on a long commute. Sometimes as much as an hour on the way home. My decision to leave was largely based on finding a job with a better commute. I was able to find some great opportunites in Seattle that allowed me to recover an hour each day that I would have previously spent commuting. If you live on the Eastside, Microsoft is a better proposition as the commute is much less.