Vantaggi
Microsoft takes great care of its employees. I feel that they invest a lot in their employees, from training to funding/empowering your projects, and they have set up frameworks to make sure your manager supports your career development. The 100% free health care/dental/vision benefits completely remove stress from that area of your life.
Svantaggi
The biggest downside of working for Microsoft, but outside Redmond headquarters, is the poor brand reputation among everyone outside Microsoft, especially in Silicon Valley. They are not known for creating great consumer services, so they are not well liked when compared to other consumer-centric companies. That cuts into the pride I have in working for Microsoft - only the employees inside learn what a great company it is. That might be fine when you live in the Seattle area where Microsoft dominates, but it's pretty hard in the field when everyone favors your competitors. Because Microsoft is such a large company, you may feel that you don't have as much control of your projects as you would have in a smaller company. They have a team and a framework or template for everything, so sometimes it feels like you can just turn off your brain and use all the resources they have set up.