Vantaggi
They work with great technologies like Django and AngularJS. Moreover, you learn a lot working with a small startup. I feel like I gained a lot of experience working there that I would have not gained working at somewhere that's established, only because I worked directly with the people that were running the company. If you are trying to one day start your own company, it's probably beneficial to see first hand how people go about doing it.
Svantaggi
The pay isn't great. I never got to be a full blown Software Engineer there, but if I had their offer would have only been 75K (plus a 9% stock bonus). It's not the place to work if you want to make a lot of money, unless you get promoted quickly.