Federico Viticci on Due 2:

The way Lin Junjie decided to release Due 2 is also worth a mention. Due 2 is a free update that replaces the old Due app on the App Store, bringing a new UI and the features mentioned above. For new customers, the app will be $4.99 as usual. For old customers only, four features will be locked with a $2.99 In-App Purchase: background sync, 45 new tones, auto snooze options, and the ability to pause timers. This is, effectively, a way to implement upgrade pricing on the App Store for an existing SKU – new customers won’t see the IAP and old owners of the app will automatically be brought into the new Due app with an option to pay for new functionality.

Interesting model, and I’m happy that Junjie was able to figure out a way to charge for an discounted upgrade. It’s a hack, but it works.