I'm trialing trialpay on a few of my products. So far no luck, which seemed strange to me(it even killed the product sales through the regular link which is not surprising when they see they can get it for free).
I went in to try it myself and found only six offers, all that required paying over $30. Doesn't surprise me no-one wants a $17 book this way... I understood there were a number of no-cost options - doesn't seem like it.