Pluspunten
Training and technical skill development are generally encouraged during your entire career. So if you are the type of person who is always looking to improve your technical skillset, it's as good a place as any for this. Other good points are that the people surrounding you are going to be some of the smartest minds on the planet. This is not an exaggeration. Because of this, on the job training at Microsoft is looked at by most other companies as a very valuable commodity. Indeed, I've had other employers head hunt me strictly based on my experience at MS without even bothering to ask me tech questions in the interviews.
Minpunten
Innovation at Microsoft has unfortunately died. The company will probably never actually fold up or go under, but if you're looking to make your mark on the world and innovate, this is not the place for you. Some of the leadership ladders go twenty levels deep (!) from the leaf node to the CEO. This means that if you are looking to be a vice president or director or some other highly placed leader, you have virtually no chance of getting there from an IC (individual contributor) roll. The amount of people you would have to leap frog is just too many. Microsoft used to be about the most secure job you could get in the tech industry. However, the latest (second) round of wholesale layoffs, that have nothing to do with the individuals' job performance, should give you pause.