Pros
Everyone is super impressive and friendly - I've never worked with a group of people that are all so kind, yet very motivated. The company feels like it has a lot of positive momentum and with the people we're hiring, it'll be a fun ride. I'd never had the experience where I enjoyed going into work every day prior to this and didn't think I was that kind of person to be honest. I do though, which is a testament to the culture and people here. A lot of ownership and your opinion will count for a lot. You'll get a lot of say in where things go which is nice. Work is interesting and cuts across a lot of domains which is fun if you get bored easily like me. Plus we're reaching into some cool ethical areas. I also like how strict we are with not contacting people on vacation and having pretty good work-life balance for a startup.
Cons
Pretty classic startup, but the company is growing and changing very quickly so you have to be someone that is ok with or preferably enjoys dealing with ambiguity and change. Probably self-inflicted since I like taking a lot of things on, but I do tend to work a few more hours than I have in some easier corp environments.