Pros
You have the opportunity to work on some many different aspects of the industry: from OS, to Games, to Frameworks and hard core research. Microsoft also support extensively their employess and give no-non sense perk, like 100% family medical coverage, paternity/maternity leave and other cool benefits if you are a bit older than a recent college hire. If you are looking for massages and free food, you will not get them here, but you will have benefits that target a more mature audience (remember, Microsofties are in their late 30s and 40s now)
Cons
Leadership do not support taking risk as much as they should in order to really innovate. The web is a new environment that requires a more iterative and risk taking approach. People who have been here are not used to this concept and innovation is hindered. The bureaucracy, or Microsoft Tax, is so high at times, that innovation is considered to be releasing a competitor feature on schedule.
