Pros
The people are great - they constantly hire nice interesting people who are good at what they do, and who also make great happy hour companions. The work is interesting and constantly changing. There is a leniency for what could otherwise become silly issues - eg: coming in slightly late doesn't matter so long as you accomplish goals etc.
Cons
They're bootstrap funded - so they lack some of the perks larger tech companies offer (401K matching is the biggest). Sometimes this means managerial inexperience as well. There is also a propensity not to promote from within - which contributes to higher turnover in almost every department. Sometimes new challenges are only met from the top down. It feels challenging to make your voice known - and in an ever changing industry this seems silly.