Pros
Microsoft provides very compelling salary and benefits. It can be very enjoyable if you find the right team. I have seen very talented people who are very enjoyable to work with. But at the same time it is very common that you find your self in a team that they are not very professional. The most valuable aspect of working at Microsoft for me is access to many smart people in all different fields. You can get an expert opinion by just sending an email/IM to the right person.
Cons
Getting promoted can be challenging and at times slow. Often I see people leave the company and they come back after couple of years and they get hired at much higher level with better compensation very different from the people who kept working in the company for that period of time continuously. Besides since Microsoft is super huge, sometimes great ideas dies in management ladder.