Pros
The company is growing quickly so there are options to move around and advance. While most work is staff augmentation, there is a decent range so that (with a cooperative manager) younger staff can gain a wide range of experience/skills. If you contract is lost, they will generally work to find you new work.
Cons
Experience will vary based on your manager. Mine was a nice enough person but it he was content to stick me with a difficult client where I had a good relationship, regardless of my desire to learn new skills. It is a body shop, just putting people on a contract. By and large you are just staffing a broken federal government office. The work generally requires little creative thought once you get the hang of it, or at least that was my experience and that of colleagues I spoke with. Final warning, nearly ALL of the work the bid and win is lowest cost, technically adequate, this type of work tends to change hands more frequently when competed.