they're useful, as long as you remember what they are. they're not your friends, they're there to get paid by you taking one of the jobs they recommended. That said, they do have connections to at least get you interviews. Once you get those interviews though, its up to you. If you get any offers, dont listen to anything they tell you at that point. All they want is for you to take the job, as they do not get paid unless you do....so dont buy their B.S. I'm your friend and this is the best path for you career-wise.
When I was looking to make a move from tech consulting, I contacted a couple of recruiters in NYC where I wanted to re-locate to. Between the two of them, I got interviews at some of the largest/best hedge funds and investment banks. Ended up getting 2 offers from 2 hedge funds (canceled a couple interviews after those offers came in). Best part was that the 2 offers came from different recruiters, so I got alot of pulling from either side telling me their job was much better than the other.