Wonderful Ideas... I'm thinking of trying just a nag screen to start that shows "buyNow", "free trial", and "continue using online"... If people still don't purchase it, then I will have to punish them more....
To see which wording of "BuyNow" or "free trail" etc works best you should do some A/B testing using something like Google Web Optimizer. Hopefully it will speed up the process of finding the correct wording/strategy/layout.