Pros
Sorry, could not find any. It's on the average of this kind of recruiting agency. Not the worst, far away from the best. If you are experienced and you negotiate then it might be a good deal. You can use it as filling-the-holes employment, or to make the first experience. If the client you work at has a good reputation you can benefit for your CV. If the client you work at meets the expectations of its reputation, then you will gain experience. After that just move somewhere else to grow for real.
Cons
No attention for any need of the employees, no help in burocracy, no guarantee of a commitment for you to get any government advantage (bare in mind that in some countries your employer applies for these benefits). They drastically change the contract upon (late coming) renovation. Payslip not clear.