Pros

They will find you work.
Occasionally, free lunches.

Cons

First off their recruiters know nothing about technology. Secondly they will bill the employing organization (the contracted project) a buttload for your services, but only pay you less than half of what they bill, unless you are great about the haggling and negotiation before signing their contract. Be careful once you are signed in, management will be completely deaf to your concerns in the event that you are pushed into work during the contract which you ought to be paid more for. They will also browbeat you over time off - There are no paid sick or vacation days, either. In reality they don't want you missing work because they can't bill the employing organization for the hours...Remember, they are making more per hour than you are even though you are the one doing the work. Employee beware.

Advice to Senior Management

Hire technically oriented recruiters so that they have a better grasp of where to place employees. Give your technicians the butter they deserve - Paid sick days, paid vacation, better benefits, 401k matching...These things are industry standards and the pay you offer is not comparable.