Pros
I was able to accomplish the most meaningful work of my career while at Glassdoor. Because Glassdoor is a relatively small company that collects a lot of data for jobs, salaries, and company reviews, there are a lot of problems to tackle, and a lot of flexibility in your approach to solving them. At the end of the day it feels pretty rewarding to know that your work can impact millions of Glassdoor users. I always felt appreciated by my managers for the work that I was doing while there as well. Glassdoor hires smart and friendly people. I really enjoyed my daily interactions with team members, and can honestly say that I learned something new from my manager or peers every week. I feel that the upper management is competent and is steering Glassdoor on a path to success. The mission of the company is noble and sincere - help people everywhere find a job they love. A lot of companies will just publish some corporate "values" or "mission statements", but I do feel Glassdoor is trying to empower people to make the best career decision they possibly can. Location - a lot of people complain that the location in Mill Valley is a negative, but if you live in the northern part of San Francisco, it can be a quick reverse commute. The office boasts serene views of Richardson Bay and Tiburon, and the free parking isn't bad either.
Cons
It's really frustrating being a Glassdoor stock/option holder right now. Glassdoor has one of the most restrictive shareholder agreements in the industry. Employees are not free to sell their shares on a private company exchange like EquityZen, nor has Glassdoor offered to buy back a portion of employees' stock (at least while I was there.) The executives claim that the reason for the restriction is so that all employees have some skin in the game, without acknowledging that it's very possible (and common) for employees to sell a portion of their shares AND have skin in the game. It's a fallacious argument, and possibly indicative of some ulterior reasoning and/or motives.