Pros
Not many, especially after the take over. But, if you manage to navigate layoffs and so forth you can maintain a career with a pretty good salary doing very little. My job duties had very little reflection on what I actually did on a daily basis. Learn powerpoint, public speaking and how to influence people in presentations and you should be able to make good money for quite a few years, perhaps until retirement. If you are really lucky you may be able to work on a legitimately interesting project, but a good chance it will never actually be used. If it does go into "production" you will almost certainly be managing contractors and creating power point slides and word documents. There are really cool things to learn and work on, but that I'm afraid is not the norm.
Cons
Umm. Pretty much all cliche's about large corporations. OK, I get it, a large Corporation is an extremely complex beast with no owners manual. Far and away my biggest complaint is to immediately stop internal development, and outsource all complex and interesting tasks to contractors or more commonly 3rd party "integrators".