Vantaggi
I've worked at many start ups over the years and User Testing is the only company I've worked for that makes me feel truly respected as a human "being" and not a just human "resource." The benefits and various perks are the most generous I have ever been offered by any company. For instance, the additional free PTO between Xmas and New Years is amazing, the 401K matching up to 5% is great, the catered Tuesday and Thursday lunches and fully stocked snack room (of healthy snacks) are wonderful and a real convenience if your day is booked. BTW I see another review saying to beware of positive reviews because the company asks people to post positive reviews when bad ones are posted. The same is true in reverse! Beware of negative reviews, including some that may be bogus, after someone has been let go by the company for cause and is disgruntled.
Svantaggi
I find the San Francisco engineering office difficult to travel to and park near so I don't tend to visit there much. While the catered lunches are great to have, I find that the menus are overly fancy, and then the food isn't up to the quality I expect. Because it's a fast-growing agile company, processes are not necessarily well known or communicated fully, often because they're being tweaked.