I've only had positive experiences with recruiters...
Not sure why they are hated so much.
Because of recruiters our salaries are always increasing and we are constantly aware of more opportunities.
Mostly the same here. Recruiters have been instrumental in several of my bigger career moves.
The only two negatives I've had, has been one recruiter who lied to me about the job title, compensation structure, and rank in the company. The same recruiter also told at least one of my coleagues about my job search.
The other negative experience with a recruiter, was one that told me that the employer had agree to my terms, when they hadn't and hen proceeded to berate me for changingthe terms at the last minute (when their agreement was explicitly in an email with the terms listed in point form).
In the case of the first one, I really didn't care if my employer found out I was looking - it meant they would try to retain me harder. Not everyone is in such a position so it definitely warrants caution - extremely unprofessional on the recruiters part. For the second one, I told them to **** off, and have never dealt with the firm since, and have steered others (big ticket candidates) away from them.