Pros
Great benefits - PTO (3-5 weeks), 2 weeks Sick Leave, 4 weeks Paternity/12 weeks maternity leave PTO, very good health plan with HSA (employee has to pay out-of-pocket until a deductible is met, company contributes too; Plan was great till end of 2012), individual office with lots of privacy - this is a great plus if you are coming from a cubicle culture, flexible hours, great infrastructure, lots of smart engineers, good pay compared to others in the Seattle area. If you can shut yourself off of the middle management incompetency and maintain a good relationship with everyone, you'll get a steady growth. Work-life balance in general is very good with 40-50 hours though it depends on the team where you may have to put in 60+ hours and weekends. Consider working for a core team if you want to be around smart engineers.
Cons
Managers push busy work. Generally incompetent middle managers - tons of politics. It's not what you contribute that counts - it is your relationship with your lead and his/her manager that weighs heavily in your reviews. Most middle managers cannot get a job outside of Microsoft - even if they did, they cannot get the benefits that Microsoft offers so they stick on. Getting things done can be a pain. Most non-core teams have incompetent team members at almost all levels. There are frequent re-organizations across the company. It is common to go through 7-10 managers in a period of 5-6 years and it affects growth badly even if you are very smart. Most managers lack the maturity to be managers.