Pros
Beam is amazing. I don't think I've ever worked at a company where everyone is so smart, so friendly, so diligent, so happy to show up to work, and also so free to actually have a life outside of work (which can be pretty rare in the Silicon Valley early stage startup scene). It starts at the top--the two co-founders, Ben and Andreas, are insanely talented while also just being great people to work with. I have lots of autonomy while also receiving great guidance when I need it. I used to think that company culture was overrated, but I've changed my mind, and it's really a pleasure to work at a company with such a strong culture. I'm not exaggerating when I say that there are Friday nights when I just can't wait for Monday morning so that I can get back to work. We're not curing cancer here but what we're doing is pretty cool and important--catching money laundering and other financial crime so as to help prevent much worse crimes. Our service looks great and customers are noticing. And for an early stage startup, compensation and equity are pretty generous and benefits are good.
Cons
You could definitely make a better salary working at a huge company, though there are obviously tradeoffs there.