Pros
Nothing beats the mission and feeling like you're part of something greater than you. The opportunity to be around so many intelligent people is extremely rewarding; you can learn quickly if you push yourself. Being there for a short while is worth it just to get some financial investment in the company and experience how it feels to have everyone you meet be impressed by where you work.
Cons
The company mission is clear, but how that transcends into yearly or monthly goals is very unclear and causes an unstable environment. The entire company is always in firefighting mode, focusing and prioritizing whatever is needed that instant. I'll be very clear...it is not the time commitment that burns people out so quickly. It is the lack of planning.