Pros
People, work environment, benefits, and stability. The people are great. They're bright, passionate, and diverse. Work environment fosters a collaborate, can-do environment. The benefits are by far the best I have seen or heard of. Finally, financial and career stability. Microsoft is so large even if the group you work in folds there is always somewhere else that needs you.
Cons
Microsoft has lost its edge in innovation. Management keeps bring up the word innovation, but if you look back at the past 10-20 years what innovation has Microsoft brought to the table? Nada. Microsoft's business model is not to be a leader in innovation, but rather a fast and very successful follower. Microsoft looks to see which business areas are successful, then pounces on them and sticks it out until they are No.1 in market share, etc. Some examples? Windows, Office, Internet Explorer... Need I go on?