Pros
When someone says to you "our co-workers are our family", this is often a load of crap. ZenPayroll really is. One co-worker helped me move. I've gone to movies and concerts with others. We've done team outings that are really team vacations. We accept each other for who we are as people. Flaws, attributes, and all. Just like you do with your family. The founders tell us that we're building this as a company to last. And this mentality permeates every decision we make. Answers aren't made up on the fly. Everything down to the seemingly smallest decisions have some concrete and methodical rationale.
Cons
Just like any other start-up, there's an expectation that you need to move fast, be brilliant, and be on your A+ game. That's the case here. There's no room for slackers or people that want to coast on the coattails of a successful start-up. This might mean some occasional late nights or weekend work, but believe me it's all worth it. The stakes involved are high, but the reward and achievement is all worth it. With all of this, though, I often feel like I'm doing the best work of my life.