I've had several experiences, most of them negative. Some have treated me like if I was a piece of meat... It had felt like working with mercenaries or traffickers... Most only want to make a quick profit out of you with a quick positioning (companies usually pay them a commission of up to 25% of your first years' salary). I've been lied about job specs, contract terms, etc.
Not all recruiters are what I would call "headhunters"... I got my current job through one that I would consider an exception, as he was the total opposite of what I've just described above. He spent a lot of time working with me to be successful in getting the job (and my salary is not high at all). At the end, we both won, but his style an attitude was extremely different when compared to the other experiences I had.