I have a contract position through TEK at a large IT company. While they check in semi regularly, there is no real management or advocacy for you with the client. They seem more concerned about keeping the position filled so they get paid, and not helping you advance your career. There are no benefits--no vacation, subsidized health insurance, retirement contribution--and the pay is below market for the actual work being done.
Below market wages, no benefits, no guarantee that you will be employed tomorrow.