How much success had you made with Revenue sharing?

I use PTC sites and Revenue sharing sites for an while now. With the advertising of my PTC Place site I got an lot of signups even on Revenue sharing sites. But the most important thing on Revenue sharing sites is gaining commissions. Rarely some signup buy some adpacks. Have anyone more success ? From my experience it works best when you make an referral exchange deal on Revenue shares, when user A signes in on an site from user B and vice versa and both buy adpacks. So both gains commissions. Have anyone an better way ? Maybe paid to signup offers ?