You've got to find the good ones.
Most are utter garbage, but I've found a few that get most of the jobs in the area in which I work and are actually pretty decent.
When looking for a new role I contact those agencies first and spent most of my time dealing with the good agents.
It goes both ways as well as they want to work for people they know they will place relatively easily, so if they've got you a job before they'll be more inclined to deal with you again.
Plus you get the perks like being taken out for free drinks by the agents as well
