Pros
Microsoft has all the resources necessary to win in the market, and you're surrounded by some of the brightest people in the world. It's like having all the smartest kids in the class in the same stadium, all wildly waving their hands in the air so they get called on next. But seriously, it is a great place to work for a while if you like a challenge and the opportunity to do something with huge numbers and impact.
Cons
Hyper competitive culture means that you spend more time on internal politics than succeeding in the market. Seriously, it was easier to gain market share with an existing product than go through the hassle of launching a new one. The wrong folks are rewarded - predicting hockey stick growth charts is critical to getting new funding - after all, nobody cares about a business that won't make a billion $ with 50% margins. So the inflated growth charts are made, funding given based on those charts, and then the 'responsible' execs move on to their next promotion, leaving somebody else to hold the bag when projections aren't met. I've seen it happen over and over. Finally, as Microsoft makes the transition from a growth company to a cash cow, there's a lot of internal dislocation and the internal culture suffers.
