Ventajas
Top to bottom, this is an absolutely fantastic company to work for. It's really impressive how great a job the management team has done of finding people who fit the culture and blend well with the current employees. More than anything else, the folks at UserTesting do a great job of empowering you to play to your strengths. I've worked at companies where middle managers try to force processes on people and stifle creativity. At UserTesting, if you have a good idea that can help the company grow, everyone around you will do what they can to help you make it happen.
Desventajas
I think as the company starts to grow more rapidly, it will be important to figure out ways to retain many of the talented people who are helping to grow it.