Enjoying this discussion. Plenty of good opinions here, and it should be obvious this is a somewhat experimental sales model, so we don’t have all the answers.
I am not really worried about it not working out. Every sales model has weaknesses. We think this one nicely balances the motivations of the customer with those of the developer. The customer pays for concrete features, and ‘owns’ them permanently when they purchase. The developer is motivated to keep the product moving to keep the customer purchasing.
I’m not worried that we will run out of things to improve and features to add. We’ve been in this business for probably 15 years, and I’ve never really seen a piece of software run up against that. I’ve never seen a developer say “we’re done!”
And I’m also not really concerned about the argument that new users get too much. Consider the existing sales models: If I purchase version 1.0 of an app, and then pay an upgrade to version 2.0, I have paid more than my friend who just purchases version 2.0 later. And yet my friend has exactly the same app I have. Is that fair?
And if I subscribe to an app for 5 years, and then my friend joins too, he/she gets the same app for a fifth the price I have paid. Is that fair?
In other words, you can’t really value an app like you value a piece of cake. If I buy a piece of cake, I can only eat it once. The moment that I eat it plays no role. In the app store terminology, cake is a “consumable”.
Software is not a consumable. You can use it as much as you like. I could buy an app once, and use it for 20 years. So the argument that the new customer gets the same app, even though over time they have paid less, doesn’t really fly. They may get the same app, but they don’t have the years of usage you have. That is what you are really paying for — the app itself is not very useful; the usage of the app is what is useful.
Anyway, it’s all largely theoretical at this point, and time will tell. The first hurdle is crossed, namely that it seems people are willing to pay for the premium features even when that is not a requirement to use the app. The other hurdles, eg, keeping them paying, are yet to be encountered.