Pros
Company is growing incredibly quickly. Everyone is pumped about the business. The day-to-day is constant puzzle solving. You're surrounded by motivated people who love the company. Relatively flat structure. You see the impact of your work on a day-to-day basis. Everyone outside of Uber is excited about Uber. Since starting at Uber, all my old college friends want to get back in touch.
Cons
Holidays are work days - be prepared to work like crazy. Your significant other must really love you to stay with you with these hours. You must love Uber to work at Uber. Management is young and figuring itself out, but CEO is one of the great CEOs of the world. He loves the company and empowers employees. The structure is becoming slightly more hierarchical which is natural for a company growing at this pace.