Pros
I worked with Preferred Solutions for 3 short term projects in 2014. They were up front about most things, and their travel department did a fantastic job setting up all the arrangements.
Kontras
One of the projects I got let go early, not because of anything I did, but because of a hospital decision about how they were implementing the software. A few people with less experience got to stay over me, and the company said it was because they wanted to have as many people as possible get experience supporting the software, so their pool of people could be bigger when they needed consultants for future projects. I felt as though they should have kept the people with more experience, and who had done a good job for them on previous projects instead. On the third project, the recruiter did offer to make it up by extending me an extra week, although I could not accept because of jury duty. So I do have to give them credit for trying to make it up.