Pros
Sidebench is a highly professional place to work, especially given it's size and scale. The community of folks there are curious and empathetic by nature, and everyone REALLY cares about the work they're doing. If you're a junior to mid-level employee, I couldn't recommend a better place to learn and develop. The management team is highly decorated and well experienced, and they allow their employees to experiment, try new things, and they trust employees with a lot of responsibility. After having worked at other organizations, I'd like to compliment Sidebench on it's sophistication and professionalism. In a startup environment, process/procedures/best practices usually fall by the wayside, but a tentpole of the company's success, and the value that employees derive from working here, is the level of execution and the standards that teammates hold each other too in their day to day work. Second to none on this front.
Cons
Agency/consultancy work isn't for everyone, and juggling multiple projects can be tough for some. Also, you're given a lot of autonomy, which can be seen as a plus or minus depending on your personal work style.