Any insights on recruitment agencies?

Management have basically just told me don't expect a pay increase or career development, while in the same breath agreeing that I'm doing the work of an entire team. Time to move on I think!

Has anyone had any joy with recruitment agencies? Esp. for Marcomms & PR ( mid career / management ) type roles that could be helpful? I've not gone the recruiter path before but finding a job myself right now feels like hell too.

Any tips on good / bad agencies would be huge, cheers luvvies.