This is based on my personal experience while resolving issues with the products of our company Interlecta, and it is not a general solution.
Start with a new product
It is always better to start with a new product. Don’t use previously created product that was free or paid – the time you could save by doing that will cause more troubles afterward.
This is mostly because the existing user that have already downloaded previous versions will have problem upgrading to the new release, either “try” or “buy” one.
Cannot get the correct version. One of the first problems that usually occurs is that people cannot see the correct version depending on whether they have purchased the product or not. The issue present almost in all cases when someone downloaded the trial and then purchases the full version – the result is that they cannot download the full version because it is not available on the screen.
Cannot upgrade. Another case would be when there is an upgrade of the release. They see the message, a notification by App World, that there’s a new version but there’s no button to download it.
Always increment versions. What we have learned while trying to resolve those issues was that the versions should be always incremental, i.e. the “buy” versions should be greater that the “try” version. Example: our Interlecta Translator trial was 1.3.19 while the full version was 1.3.21. That makes sense from database design point of view, but it’s not convenient at all, and such behavior is not documented, you have to learn it from experiments.
Problems with upgrading to full version
This is a common problem.
Canno upgrade to new release. If you have new release of your Try’n’Buy product people will receive a notification but when they go to the product screen at App World they will not be able to do the upgrade simply because there is no button for doing that. In our particular case there’s only a button to install the trial version.
An experiment worth trying. What we’ve found out is not a solution, but is more like a work around, it’s annoyingly slow process, but it’s ate least something that may help your customers. In short, you have to: Remove your application from App World; Remove the App World itself; Reinstall the App World; Login to App World through PayPal; Reinstall your application. It also involves rebooting your BlackBerry 4 times. That’s not convenient at all, but was the only was for me to get the latest full version.
More details were posted on our company blog at http://blog.interlecta.com/?p=466.
There’s also discussion at supportforums .blackberry.com forums: http://supportforums.blackberry.com/t5/BlackBerry-App-World-Development/Try-and-buy/m-p/232573.