Pros
In my experience, Mondo does a fantastic job of working with contractors and the companies where contractors are employed. Mondo did an excellent job of matching my skills with those needed the company where I have been placed. The Mondo staff went above and beyond during and after the interview process to smooth the way for my employment. Imagine a staffing organization that sees fit to hold a downtown parking place for you right across from the building where you will be interviewing. Mondo did that, and more. I highly recommend Mondo for anyone seeking contract work in a technical field.
Cons
Since Mondo is a staffing agency, and I am a contractor for one of their clients, I cannot report any disadvantages to working through Mondo. They simply do an excellent job.