Pros
I worked for ClearAvenue for about 6 years and had a great experience. During my time there, several people lost their contracts due to normal government contract churn and I was impressed by how long clearAvenue kept people on staff working on proposals and performing other overhead work. I would have expected a small company to be less able to handle these situations but they kept people on much longer than major consulting companies. The CTO can be a tough negotiator but I think is also pretty fair. Probably the best thing about the company is the quality of the technical personnel. It is a joy and makes work so much easier and fun to have genuinely competent coworkers.
Cons
Any cons I can think of would apply to any contracting small business, if you lose the contract you are working on, depending on how things are going otherwise in the company they may have to make tough decisions, but as mentioned above, I was impressed with generosity that was shown (although I am sure those folks were worked extremely hard on proposals).