I’m going to add my voice to those calling for trials of App Store apps. Here’s how I could see it working:
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”.
If you install the trial app, it gets flagged with a “Trial” flag over the icon, in a similar way to the “New” flag that was introduced in iOS 6.
When you run the app, it permanently runs with a double height status bar, which shows the amount of time left. Tapping this status bar opens the app store page allowing you to purchase the app.
Once a trial is used up, you can’t get a trial of that app again on the same Apple ID. When the trial is used up, the app icon still remains on your device, but the flag says “Expired” and tapping on it takes you to the App Store rather than opening the app.
To any developers reading this: I posted it as radar 13197637 (OpenRadar link) — please feel free to file a duplicate!