Vantaggi
For type A personalities that can handle the politics, you can make a very good living. The benefits are amazing. The Redmond campus is is very nice place to work. Your experience will depend greatly on the group your wind up in. For those fortunate enough to hook up with a good group, and get a good manager, MS is a great place to work. The company's core businesses, Windows and Office, still provide a near guaranteed flow of profit. There is no worry about the company hurting for cash anytime soon. If the offer is from the right group, and you can handle the politics, then I recommend giving Microsoft a try.
Svantaggi
On the other hand, if you get a bad manager, or wind up in a position that is a poor fit, your career at Microsoft will end swiftly even if you have a long history of strong performance. Every year, 20% of employees are given poor rankings (forced distribution), effectively ending their career at Microsoft. The forced stank rank distribution ensures that half off all new hires are gone within 5 years, and will not vest the majority of their stock awards. Discount the value of your job offer accordingly. Microsoft is a giant company, and it's nearly impossible to be more than a small cog of the machine. If you're looking to be a force for change, look elsewhere. If you try to change the company from the inside, you're more than likely going to make enough enemies to end your career. Although the company is still a top employer, many of the very best programers go to Facebook or Google if they can.