Pros
Everyone at Mighty Engine has an interesting personality. The stress involved in a small marketing firm is offset by the joking around and the sense of camaraderie. There was, at least in my web developer position, lots of room for self-management, which was nice. A very flexible company in general, especially with things like doctors' appointments. At Mighty Engine, there seems to be a sort of trial period where management seems scary at first... but after getting to know you, they place a lot of trust in you and listen to your opinions. Employees are valued for their personalities, which shows in moments like birthday lunches. Also, it's a good place to work if you're worried about being too much of a weirdo for an office job :~)
Cons
Limited opportunities for technical mentorship — which is just 75% "con" because it just meant I had to learn how to self-educate. Also, design work seemed to be a bit stressful and involves staying late.