Pros
Uber truly believes in the concept of "best idea wins." It doesn't matter how long you've been at the company or what level you are, if you have an awesome idea Uber will let you pursue it. The people here are insanely smart, innovative, and passionate. It's incredible to be a part of such rapid growth and see the impact of what you're working on immediately. There's of course starting to be growing pains, but that's part of what makes it so invigorating and such an interesting place to work--you don't necessarily know what's going to be happening next. I was at Google for almost two years prior, and despite how much I loved it, I can't imagine being anywhere other than Uber.
Cons
You have to be very comfortable with ambiguity. Changes can happen fast, and you have to be willing to be on board and adapt fast. If you need structure, this might not be the best environment.