I've used them to find students and found their service to be quite good.
Depending on your location, lesson fees etc, you might have to wait a while before you get contacted, and you might get the run around even when you do land a student (from the students, not the site).
Mind you, I have got some excellent students (present tense) from them so I think it is mainly a matter of waiting for good ones to turn up.
Give it a go. The students pay a fee for teacher's contact details so it won't cost you a thing.