Before I entered the Jesuits I temped for about nine months, first working for Paccar (the parent company of Kenworth and Peterbilt trucks), and then 6 weeks for Microsoft. It wasn't a bad experience. The upside is you get paid weekly, pay is a bit more than what you'd make working for the company itself, you have flexibility if you want to take some time off between contracts if you want, and long-term contracts are definately a possibility if they like you. Oh, and it's a way of getting your foot in the door of a company and impress them so they'll hire you.
Microsft treats their temps very well. I was paid very well, got a free bus pass, free soda and coffee while on the job, and they will pick up a taxi fare if I had to work late. You are, however, made to feel like something of a second-class citizen (Microserfs, the joke goes...)
The downside is no benefits (though some of the more enlightened agencies will provide discounted health insurance), no sickleave (no work no pay), and you can be terminated from the contract at any time and for any reason.
Most people sign on with several agencies. Whoever comes up with something first is the one you take. Just tell the others you're already on a contract.
The customer isn't a moron, she is your wife -David Ogilvy