Pros
the team is quite experienced, with large percentage having worked at prior startups. Experiences are quite diverse and from all over tech industry. No large companies' bureaucracies since team organization is mostly flat (no multiple mid-level managers, we regularly talk directly to ceo about all business aspects). Company is pretty flexible with where you're working from, as long as you can work independently.
Cons
Since its relatively early/mid stage startup (3-4 years only), company still not generating any revenue. So, no benefits like an annual bonus, though they make it up with generous base salary and lots of stock options.