I've heard good things about Adecco from my mom, who temped for them in the mid- to late nineties as an accountant. I'm sure a lot has changed since then, but she had a good experience. They gave her three assignments at major companies, and she was offered a full-time position at all three. After declining the first two, she accepted the third.
I'm starting with Adecco now. Hearing the news about their shifty behaviors and policies on the internet makes me wary, but my experience thus far hasn't been so bad. They found me a temp job, but it took a while...perhaps because I wasn't pursuing it myself on my end. I've registered with Adecco in Columbus, and nothing much happened with them. They would call every once in a while with job opportunities on an assembly line in New York for about $9/hr, or once they had a jobs event with prospective employers, but mainly just months of nothing. I moved to Cincinnati for different reasons, and eventually registered with the Springdale office. The representative was very friendly (didn't talk with representative in Columbus, just registered online). He got me a job pretty immediately, entry level for $13/hr (about $27k/yr, if one works full time for a year). I'm thankful for the opportunity, and the salary.
One thing that put me off was something in the Adecco forms they want you to fill out. One makes you waive your legal rights, should any professional disputes crop up. All disputes will be handled within the agency; you can't go to the government. Maybe Adecco is just doing damage-control--if a company thinks their temp is likely to sue for sexual harassment etc. to make money, they don't want to hire temps from that agency. Still, it's really bracing to see that form and know that Adecco wants you to waive all your legal rights in this area. You can opt out of this system by e-mailing for an opt-out form within 30 days after signing the waiver.