Pros
This is a team full of super-smart rockstars who take obvious pride in what they do. We get to work on industry-leading technology and get to collaborate with other companies on exciting projects. I've watched our technology advance by unimaginable amounts! We have opportunities to advance ourselves in technical and management aspects, and the senior leadership is very accessible. Striking harmony in one's life is important to management, and the company is receptive and supportive of employees' needs. The company has a culture of problem solving, and that is woven into most aspects of operations.
Cons
We work hard, and some deadlines result in company-wide crunches that are draining, but haven't killed us yet. Standard concerns about start-ups apply, but we've reached a stage where lots of those concerns have been mitigated.