We just signed up with them about a month ago. I run 2 franchises; Honda & Hyundai. We pulled the radius in very close (7 miles for Honda, 10 for Hyundai) so we wouldn't get flooded with such a high number of leads. So far, they seem to be working well. Just make sure your bad lead rejection settings are set up properly (especially if you have dealix or another paid lead source).
I've also come to find that sometimes, with vendors, what comes in as a "new car" lead actually turns into a used car lead (which is fine - I'll sell them all!).
I haven't really had them long enough to be able to tell you how "filling the pipeline" is going -- touch base with me in a month or 2 & I'll have some feedback.