My experience has never been good or bad. I have used two providers, one is one of the largest located in Indy. It seemed to work best for financial sites.
Ummmmm ... by financial I mean like payday loans, debt consolidation, bad credit, sub-prime type marketing.
It also works best when fed to a portal type site. Something designed similar to a parking page. 30-40 buzz word text links with a 30-35 character pitch line. You've got about 3 seconds with a pup to catch their eye. You can't sell them anything in 3 seconds but you can induce them to click a link.
It's similar to what I've heard you tell people a hundred times about link dumps. Be creative and use alluring text for your link captions and pitch line.
That's my experience, as always,
results may vary 
Regards,