Pros
Some interesting problems and access to information about the projects of leading companies. Because the company prefers people without expertise, it is easy to pick up a year or two of resume buffering experience in things like machine learning and data science or whatever else you like. A few good eggs. Low standards.
Cons
Non-existent mission and vision. Little understanding of competition in domain. Promotes or retains those that are most self-serving and preserves the egos of the founders. Encourages quick execution of substandard and faulty work. Drives away their best. Most middle management can't be trusted to listen or communicate effectively (some lovely exceptions). HR has a habit of lying. Odd hiring choices. Founders are mainly chasing funding.