Pros
You get to work with other startups that are doing creative work. The company is trying to solve a problem of connecting developers with companies / startup who need to find developers quickly.
Kontras
Not much interaction with the employees at the company as most of the time is spent working at client location. They do have a team that works does software development in house, but if you are hired to work at client location, most of your time will be spent working out of office and you will hardly interact with the team.