Pros
Ok, so I never would've thought I'd be working in insurance. Boring, right? But once I learned about it--using data science, technology, mobile-first UX, gamification, and branding to create something radically different than anything else out there--I was sold. Unlike everything else in the industry, we're actually going to give people incentives to to the right thing--and therefore, actually change society for the better. It's an idea whose time and technology have come, so if doing something you can feel good about matters to you, this might be the place.
Other good things: really having a chance to influence the future of the company, since at this size we all either report to one of the founders, or to someone who does. (Having come from two giant companies previously, it's hard to overstate how different this feels.) Ton of funding means no stress that we aren't going to make it.
Really smart, driven people out to do great work; interesting mix of people from more varied backgrounds than your typical startup--but no egos, no a-holes. Also, since a lot of us have families, go snowboarding or ride motorcycles on weekends, there is actual work/life balance, which is pretty unusual anywhere people aren't just punching the clock. Also people are cool about flexible/remote work--which I think comes from mutual respect and being able to count on each other.
Great pay, convenient location downtown, impressive views, plus lots of standard startup-type perks like catered lunches, gym reimbursement, sit/stand desks for everyone, whatever workstation you want (one of our back-end engineers is rocking a 40" monitor), snacks, Blue Bottle & Peets, shower & bike parking in the building . . . I'm probably forgetting something.
Cons
--No equity.
--Absence of processes/shifting priorities (standard startup stuff)
--Too much to do
--Largely accidental culture thus far, no reviews/growth plans, etc. (we just hired an HR person, finally)
--Insurance regulations affect various aspects of product, marketing, etc.