Pros
Very often, recruiters have direct connections to the hiring managers at various companies- people that you would never be able to get an audience with otherwise. These hiring managers get 100 resumes on their desk every week, but when the recruiter they know and trust calls, they pick up. Recruiters are dialed in to the specific roles these hiring managers are looking to fill, so they have their pulse on what's available right now.
Cons
Sometimes, a recruiter that is hungry enough to get someone hired will compromise their morals a bit and have you interview for a position you have no business interviewing for. If you are in the interview or on the phone with the company and realize this- courteously tell the potential employer that you may not be suited for the position they're hiring for with your skillset or experience. The interviewers will appreciate your honesty and may even pass you on to a different department where you are qualified. DO NOT attempt to talk your way into a position you're not qualified for. It will only backfire when you lose your job 2 weeks down the road for not being able to complete the requirements. Ask questions during the interview to get down to exactly what they are looking for in a candidate.