Pros
If you're an engineer, there is some really interesting work you can do. You have access to technology that few people ever get to touch. The offices and perks are great as well
Cons
Political fights in upper management are destroying the company. As an engineer, expect to be told that everyone is working on some massive initiative across the company. Everyone will drop what they are doing to work on this initiative, and four months later there will be a re-org and you will throw out all the work you've done. You'll repeat this over and over, and each time management will tell you this re-org is different. Also expect layoffs almost every year around November, only for the laid off people to be replaced by acquisitions. Also expect your project to be killed and replaced by an acquisition that is also killed a year later. Just really don't expect to ever ship anything or accomplish anything.