Pros
Work for an innovative product and with highly talented people.
A very young and cohesive team. Many opportunities to build connections and friendships outside the office.
Cons
I have witnessed many people getting fired because they disagreed with management, their performances weren't up to expectations, or because the company simply didn't need them anymore.
The financial situation is far from stable: the company is constantly and desperately trying to close that one deal that would allow it to survive another year. Once, due to financial troubles, employees did not receive their salaries for three months.