Pros
Good pay.
Good benefits--really good health, eye, dental, and life insurance options. 401K. etc. Bench policy (if the client org has to drop you on short notice, you still get paid while Resolvit places you elsewhere). They have a great educational stipend. I've used it for several classes and books, all of which benefit me and my resume.
Friendly and helpful "handlers." They're great about checking in on us and making sure all is well with the work and the relationship. They pretty regularly take us out to lunch. Requests -- for benefits info, forgotten passwords, insurance help -- have always been handled very quickly (like immediately).
This is the first "boutique" staffing company I've worked for so I can't compare to others; however, I've been very happy working for them. As a contractor, I work for (and at) a client company. I love the client company they placed me with. Most of my coworkers at the client company also work for Resolvit. We're all happy with them. It's great to be given the leeway to integrate with the client org as I see fit, and not be micromanaged. There's a lot of freedom and trust.
Cons
I have no complaints, but there is a twenty word minimum for this field, so I'm going to keep typing.