Pros
Company moves fast and you can be very productive. Minimal bureaucracy. Generally good at attempting to disseminate vision from top-down. Strong technical contributors and great peers. Most policies and practices are employee-friendly (in that there's little impediments to getting stuff done). Company does get rid of low-performers regularly.
Cons
As with many rapidly growing organizations, there's some chaos and politically-biased positioning during the changes. Some managers are focused too tactically on product today, not strengthening the team and products for future. If you need to work at a place where things don't change much or where you can know you'll be employed for years--this is not the place for you. Work load can be heavy at times (but the work itself is interesting and fun).
