Pros
The work is interesting and fun, the people are smart and talented -- at this point (~3 years in), I feel like I work with all of my friends. I come to work early because I feel so pumped about what I'm doing. The companies we partner with are some of the most exciting, ground-breaking ones out there. And the perks are pretty good too, if you like snacks and comfy couches, (but hey, I'm easy). Even if a new employer were to offer me 2-3x what I make now, I don't think I'd take it.
Cons
The biggest con is that you can never work anywhere else again because nothing will compare! While that is fairly accurate, there are a couple downsides. The open office can be pretty distracting, and the company doesn't have the clearest stance yet on working from home. I also think that Wistia, like many startups, has a lot of ambiguity. So you have to be comfortable with ambiguity and change or you'll be frustrated.