Pros
The benefits are great (I think). I do not have a whole lot of work experience, though. I've only had two jobs since I finished my undergrad a little over 5 years ago. There are a lot of resources for employess: wellness center (workout facility, massages, accupuncture, etc.), employess assistance program (for those in need of financial or mental help - among other things), volunteer opportunities, etc., etc. There is a 403(b) that matches anywhere from 4%+ (depending on position and years of service, I believe) as well as a Defined contribution plan which is a percentage of your salary based on position and years of service, as well. Plus we have been in the top ten of the Fortune 100 Best Companies to work for for the last few years - I personally think it's kind of a fluke, but they must be doing something right.
Cons
Appears to be quite difficult to transfer within the system. There are new rules defining how an employee must go about the process: inform your direct boss FIRST, then if you are invited to interview in another department/entity, etc. your boss is informed and can decline to allow you to interview, long process that your current boss can drastically slow down.