-work with lots of intelligent people
-autonomy in working on complex projects
-feedback oriented culture means you have an impact
-culture of transparency and ownership
-top-down emphasis is placed on diversity and diverse hiring
Fast-moving startup with a ton of interesting problems, a great deal of ownership over projects
Collaborative environment with a team willing to learn and grow together, which is just awesome to experience
What an amazing team! A bunch of smart and kind people. The founders are incredibly open, transparent, and approachable. Everyone is serious about work-life balance (very unusual for a startup). The technology and general area is really interesting (not to mention hot right now!).
Cons
You have to be able to juggle a lot of different projects. I think this is typical of startups, though.