Pros
Little higherarchy, lots of responsibility and opportunity. If you work for the right person/department, it can be a great place to work and learn. Mostly a casual atmosphere, and there is always a get it done mentality. In the right groups or departments that are properly staffed and have good management attitude, it can be a great place to work.
Cons
It's loosely organized which can be a positive or can be a negative when things get out of hand. There can be frustration in lack of guidance and direction. For some departments with the right people and leaders it works well, where others do more poorly. There can be a lot of snap judgements and whiplash back and forth when some more planning and foresight overall could be beneficial. You can also get the whisper at the top turns to a shout at the bottom (rigid conveyance of orders/information) with some leaders, where others are good about adapting to situations. It all depends on who you work for, as I'm sure is true with most organizations. The performance bonuses are all supposed to be customized to every individual, but after several years working here, it seems like most people are on a promotion/raise schedule. There isn't much feedback to be able to differentiate. It is hard to tell if you're really doing well and if the "you're doing a good/great job"s are significantly reflected in your compensation or not; I'm guessing long term they will be. From colleagues with the same experience I do, I would guess base salary is middle ground and bonuses are on the low side, especially considering the extensive vesting time (5 year cliff vest).