On some of the sponsor programs we have tested we saw 10-25% incress in signups, however too soon to tell about the recurrings, and credits/chargebacks yet. That said we have also seen paid trials sign better than sites with no cost 30 mins trials. Comes down to the product you sell and the way you market it
Epoch has a good crew, they know what they are doing - they have really taken some good points on the overall best processor list for their latest features
