Pros
Inclusive and supportive culture, parent-friendly, mentorship, genuinely interested in developing my personal/professional goals, lovely offices, transparent management, trusting, smart and fun colleagues, inspiring CEO. Not to mention free gym, yoga, open restaurant every day, an incredible selection of food available whenever you like, great coffee, conference budget, craft beer on tap, sponsored beer club - so many clubs, great parental leave benefits, rock climbing wall, frequent events and celebrations...
Cons
As with many startups, the organizational structures in place are pretty loose - this personally suits my work style, but it's not for everyone. Everyone is figuring out stuff as we grow (so fast!) and it can be hard to feel on top of it all.