Pros
Dropbox is almost a parody of itself, but in a good way. It can be hard to see the real culture from the outside beyond the awesome food and the cool office decor, but both management and engineering really care about making a top-notch product (and having fun while doing it!), and there is a ton of transparency, openness, and trust in the process. The employees here are generally great people, smart, fun to be around, and skilled engineers.
Cons
It will eat your life, if you let it--actually less because of the sheer amount of work and more because the environment and culture puts a lot of emphasis on spending time with and being friends with your colleagues, which makes it very easy to socialize only with co-workers. You may have to work to maintain your outside relationships and activities. We're trying to hire as fast as we can, but it still isn't enough--some product areas and departments within the company are understaffed, which can cause constraints and dependencies and generally keeps us from living up to our full potential.