Pros
I am currently working at my first assignment for Aerotek, and have been pleasantly surprised by my experience. Having spent several years dealing with other contract/temp agencies where the contract staff is treated like garbage, I was amazed at being treated like I'm worth my weight in gold by my Aerotek recruiters. Within a week of meeting with them, they had me out on interviews, and within two weeks I had an assignment making more than I did at my last perm job. It has been a really pleasant, stress-free experience. They did all the legwork, got me some great opportunities, and all I had to do was land the positions. That's what a temp agency is supposed to do. Too bad most don't!
Cons
The benefits are garbage, but that's pretty typical for temp companies. If you want good benefits you pretty much need a perm position. The communication regarding holiday hour changes between my assignment, my recruiters, and me was bad. If other employees hadn't told me about upcoming office closures, I'd have showed up to a locked building. (My managers and recruiters never reached out.)