I've just installed MindNode, after re-reading Paul's enthusiastic recommendation. And lo and behold, what do I find? It allows owners of previous versions to upgrade effortlessly, provided the previous version is installed when you upgrade (so the new version can "find" it).

This is a huge step forward! It shows that upgrading is indeed a viable option for App Store products. I'm delighted! I shall write to John Gruber immediately.

Cheers!
Bill

I had the same (pleasant) experience with MindNode -- but I think it's due to some spoofing they managed to pull off. I don't believe the App Store actually supports "upgrades" across the board, but MindNode made it appear than an in-app purchase was an upgrade. Or maybe the other way around, made an upgrade appear to be an in-app purchase.

Whatever it was, it was surprising and clever.

I suppose the only way they could pull it off is by being able to check that you've got a previous version of MindNode on your machine - if you didn't, and if they'd already pulled the early version from the Mac App Store, then you wouldn't be able to prove you'd had an earlier version in the first place (except maybe by sending them screenshots of your list of "Purchases", copies of Apple invoices etc.). So the MindNode solution depends on having earlier versions of the app in the store, which must be awkward to manage from their point of view.

I still think it's a brilliant idea!