Pros
The work is usually very interesting. Some equity is provided, so you are exposed to the potentially large upside if the company succeeds.
Cons
Things can be very chaotic, which is perhaps to be expected from the rapid growth and extreme timelines the company puts itself through. The Pareto Principle is very pronounced here. There are a couple of employees who really drive cohesion and functionality in the company's software through the chaos, crazy timelines, etc. For the people who are making these systems function the work/life balance is rough, and the compensation is not correct--it appears that, for employee retention, the company banks on the novelty of the overall mission and the potential for long-term upside for employee retention.