Pros
As the first startup job I'd had, I was star struck. The perks were great! Lots of swag! Happy hour is a blast each week, and a great way to unwind. The flexibility in hours and the ability to work from home (or around the world) was honestly unparalleled and not something I appreciated as much when I was there. Everyone was always easy to get along with, and I usually enjoyed being in the office and chatting with my coworker's, as every person has really unique backgrounds. The good designs that came out of the platform were incredible, and we did bring opportunity to quite a few people across the world, both designers and customers.
Cons
Now, the cons. In the few years I was there, the company went through rapid amounts of change in product and people. The other reviews of nepotism are spot on - forget hard work here, it's not rewarded. There is no rhyme or reason to how people move up, and positions seem to be randomly created based on personal feelings and not skill or performance. Going off that, growth is extremely limited - even if you're promised the opportunity to grow, it rarely manifests. Also, feedback is worthless - product asks for it, but it rarely grows into something that is actually intuitive for our users, as the focus is more on making things "pretty" rather than user friendly. Lastly, the big one is that I'm pretty sure a lot of what we did is illegal. We have no in house counsel and no compliance teams, but regularly deal with copyright and trademark issues. If a copyrighted image is sold to one of 99's big clients, their pocketbooks are bigger than ours and the company will be screwed.