Pros
Extremely progressive company and with great people. All the managers and the VPs are brilliant, approachable people. The company culture is awesome without teetering over to (TV Show) Silicon Valley-like excess. As for technical aspects, the engineering culture is extremely strong, as a result they have very good practices and almost no code-smell. Perks wise, dinner everyday and lunch every other day. Solid snack area. Fully paid health, 401k with no matching, HSA, and other minor things like yoga classes.
Cons
It's still a start-up, so the time pressure and stress is still there. It's much better now than it was when I was still working there, since they've hired a lot more people. But you shouldn't be joining a start-up expecting to rest and vest. Not sure where the company will be 2 years from now. Plenty of competitors. And a product that is effectively a commodity to most non-techy people.