Pros
Staffing agency, not a recruiting agency. It's easy and fast to get a contract job there if you have the qualifications their client is looking for. Literally you just talk to them on the phone and they send you for an immediate interview with their client.
Kontras
Since you're on their payroll and not the actual client, you basically have zero benefits, state required minimum sick and vacation days, and you're only getting paid a fraction of what they're billing their client on an hourly basis for. You CAN purchase health insurance through them, but it's not a benefit when they're selling it to you with a profit. They might be a good stepping stone to get your foot in the door at a company that you want to work for, but there's no reason to really want to work for them.