Recruiters will be able to tell you very basic information about the working place (i.e. office hours, dress code, number of holidays, size of the team etc.) - all the things that you can easily find out for yourself. And keep in mind they are NEVER going to say something bad about the company. They are trying to sell the job to your so they can get their commission.
On top of that, the recruiter needs to be paid one way or another (in the UK they usually get paid a percentage of your salary over 1-2 years). Although recruiters are usually paid by the employer and not the candidate, it still means that to an employerer a candidate costs less to them if they come directly rather than through a recruiter. Hence you will have a harder time getting a higher salary if you go through a recruiter.
They are nothing more than middlemen and you are doing yourself a disfavour by using them if you do.
The vast majority are crap. The really good ones are worth their weight in gold.