Pros
I was a contractor for a DoD department in another state from the DTSI home office. Of the DTSI personnel I only ever met my manager, and had only occasional need for communications with HR. All my interactions were supportive and professional. I feel that the DTSI administration had my back and went to bat for me and the other contractors on my team. The healthcare benefits were good and the company went beyond expectations in covering the employer contribution. My 401(k) was 100% vested from the start.
Cons
The auxiliary benefits provided by DTSI (dental, vision, STD, LTD) are through a cut-rate life insurance company that is run like a fly-by-night operation. Contact with the insurance company representative was through a Gmail account and the policies were very haphazardly administered.