Pros
Some very smart, talented nonmanagerial employees who work very hard to benefit the company. As a startup, there's always lots to do, so you'll never get bored. Room to grow as an employee, if not in terms of title/salary, at least in terms of taking on more responsibilities. Depending on which team you're on, work hours are pretty stable.
Cons
Very poor internal communication. No remote flexibility, many employees are severely underpaid, benefits are very limited, and raises/promotions have to be fought for tooth and nail. There's a lot of dishonesty and a real lack of integrity, especially from management. Nearly everyone is unhappy, and management does not trust each other or subordinates, which has created a tense, negative, stressful work environment. Serious HR complaints are routinely dismissed. CEO believes his knowledge always trumps employees', despite their experience or skills, and is closed off to new ideas. There's a real sense that employees are seen as numbers, not people. Unless you're great at compartmentalizing, working here can become incredibly depressing.
Prior to joining, I assumed the reviews here and on the Social Annex profile were only from employees who weren't cut out for startup life or who had one bad experience. I can assure you that, unfortunately, the sentiments above are shared by most, even those who left on relatively good terms.