Very nice team, family-like atmosphere, interesting technology and ambitious vision. Work time is flexible (goes both ways, but I list as Pro). You're going to learn a lot about mobile ecosystem, network stack, data analysis. Benefits are very close to top-level big companies. Next to the office there are plenty of good restaurants, and delicious donuts.
Cons
Work can get really intense at times. It's a startup so it's expected, and it's on reasonable level.