Amy Worrall, on her blog:
Developers can choose whether to allow a trial of 1, 7 or 30 days, or to disallow trials all together, on a per-app basis. For those apps that allow trials, the App Store would show a “Try for 7 days” button alongside “Buy app”.
I won’t spoil it for you, but the rest of her idea is very solid. It feels exactly how Apple would do trials. On that point, Apple will at some point have to add trials and upgrade-pricing to the App Store. Since Amy contributed a perfect implementation of trials, let me give Apple an idea for upgrades:
The developer attaches a piece of metadata to a new app, telling Apple that it is an upgrade of an older app. When you visit the App Store page for the new app, Apple compares the new piece of metadata with your purchase history and determines your eligibility.
I silently wonder if the reason Apple hasn’t released new versions of iLife and iWork is because they haven’t rolled out upgrade-pricing yet. Lazy bastards.