[GraemeJ]

Although the subscription model does offer some advantages, on balance, I think I'm with jeffn1 and would prefer simple up-front payment.

Beta testing is never 100% proof - plenty of software houses have found that out . There is always going to be a risk potential with software upgrades, particularly where major re-coding has taken place.

I appreciate the fact that you have told people they could upgrade for free - a great offer on your behalf, but hardly very business-like. Here's an alternative model, used by other houses. Offer the product at a price, but not charge anyone who registered/purchased the earlier version within a set time frame before the release of the latest version.