Pros
Phenomenal internship program. This kind of thing shows that Microsoft can be serious about investing in people. I really feel like I owe my current career path to Microsoft, and that's just pretty cool. As a full time Microsoft I felt like I had to give back and mentor interns -- paying it forward! Not all my managers / peers were great but I did have the pleasure of working with some super ones!
Cons
It did feel unnecessarily corporate and bureaucratic sometimes. Hopefully since I left the company (to check out a competitor) they're learning that speed and flexibility wins and are figuring out how to harness their strengths to reduce employee frustrations. Also perhaps as with any large company, there's always some political posturing which can be annoying. The less of that the better because fyi, your customers don't care about your internal politics!