Pros
To expand on the title - People here are awesome. Everyone's enthusiastic, smart, hardworking. You know how in most companies there's always someone people avoid working with, because they're lazy/incompetent/has a terrible attitude? Here, I can't think of anyone like that. We're really, really careful about who we hire and it shows. People care about the work and people care about each other. Oh, and we like each other too - people make fast friends and hang out at and outside of work. The leadership is really outstanding. They're approachable, shockingly intelligent, and express our company's vision very clearly. They encourage challenging the status quo because they do it themselves. I don't think there's anyone who doesn't have the utmost respect for the people leading the charge at CK. The product is another great reason to work here. You can work at a great company with good perks, culture, etc, but if you're not contributing to something that will have a positive impact on people's lives (or worse, if you're doing something that you know actively harms people - those companies absolutely exist) you don't feel all that great at the end of the day. We're trying to make sure our product helps people in better and broader ways. And it feels pretty sweet.
Cons
This is a startup. This means that processes are fluid (but getting tightened up) and there aren't really training or orientation programs. And we're growing really quickly, which means that we don't all know each other anymore, and we're making a lot of changes to office life that are hard to adapt to - new processes, changing this or that IT thing. Promotions depend on what group you're in. Some teams have frequent promotions, and some just...don't. If title is something you care about, though, it's just something you have to make known and your manager will help you work toward that. Still, it would be a little nicer to have more structure around career development.