Hands down, the most un-ethical, worst recruiting company I have every worked with. I was pressured to accept a contract job before I had even been given an offer. Like others said, they pepper you with an excessive number of phone calls. They claimed that they had a company ready to make an offer but needed me to accept it on the spot or I would lose it (exploding offer). After I told them I would need to think about it and was busy that day they continued to call.
Because of this experience I did some research on them, which, in retrospect, I should have done before interviewing through them. From that I came to the conclusion that this would be a very bad company to work through and passed on the opportunity because I would have been forced to work through them. We didn't get to the phase of having to negotiate a contract, but based on what I experienced and other reviews I'm sure that would have been a very painful experience that had a strong chance of killing the deal.
It's a shame because both the end client and I would have liked to work with each other, and they had multiple openings that would have been a good fit. In the end neither one of us wanted to work through this recruiter and would have been forced to on the deal. There are some 3rd party recruiters that can really help you as a candidate. This one will actually hurt your chances of working with a company because you would be forced to work through Mondo on a subset of open positions, add negative value to the equation and ends up being a lose/lose for everyone involved.