Pros
Smart people; interesting work; impact and reach; ability to change careers but stay with the company; great benefits; great product; fun projects; accountability; awesome colleagues (not just smart but good people); opportunities to travel or relocate if that's important to you; flexible work practices; the ability to actually impact the lives of millions of people
Kontras
lots of hours; sometimes lots of ambiguity; extremely matrixed environment so you have to be very adept at navigating and working cross-group; you're impacting millions of people so if you make a mistake it reverberates; the stock market doesn't value the company as well as it should, so your stock doesn't reflect what a great company it is; people love to Microsoft-bash - you'll need to grow a thick skin