Pros: The environment was supportive. At least in the group that I was working on, people seemed pretty happy with their direct leadership. If one was interested in Microsoft, now would probably be the time to join, given the shifts that are occurring. (Note: this applies mostly to software engineers, since they are gutting some positions in order to reach a certain ratio between developers and PMs.)

Cons: You can notice the dead weight at times. It definitely seemed like Satya Nadella, the new CEO, was trying to take the company in the right direction. While I would bet for them succeeding as opposed to against, you can tell it'll probably still take a decent while.

Pros: Challenging and interesting. Really get into the dev process at the company.

Cons: A bit overwhelming in the beginning.

Pros: You typically stand at the frontline of technologies. You have relatively easy and direct access to the source code, spec, and the people who wrote that code. You can get information outsiders may not get. There are also a lot of training programs and knowledge sharing through various technical discussions. In one word, the best place to learn the Microsoft technology stack (of course). You get a chance to work with smarter people. You benefit from it by pushing yourself beyond your limits. Of course, you also have to work with mediocre ones as well. Great benefits package.

Cons: With the expansion, there's more and more bureaucracy and politics, and less and less innovation. Now there are plenty of people working on internal development and release processes, rules, and guidelines; way too many of them are invented. There are redundancies and waste of resources, both by developing them and time spent to learn and adjust to them. Every couple of years, there are definitely new internal tools and processes replacing old ones with no good reason. Now it is evident that to advance your career, you need to go with the managerial track, where senior technical people now spend time doing administrative work. Also, people good at the political game get promoted fast. People can argue this is inevitable to a big company, but no one can argue this is a good thing for a technical company.