According to a recent TUAW — The Unofficial Apple Weblog post, Apple will finally allow developers to distribute, in essence, trial-to-paid versions of apps. As a user, you will be able to download an app for free and pay to upgrade features or to simply upgrade to the full version from within the app. These demo-to-paid versions of apps should start hitting the App Store soon.

This is a win-win for everyone, users and developers. Try before you buy apps have been around desktop computing for ages. Currently, if a developer wanted to offer a try-before-you-buy iPhone app, under the current Apple developer guidelines, they had to offer two versions of the app — a full-blown app for sale and a “lite” version that’s either ad-supported or with fewer features. They were considered two different apps with regards to numbers and ratings. As a user, you’d have to delete one app and install another. With no easy way to share data between the versions, this often meant that you lost the app’s data during the upgrade.

Now, we’ll be able to download one app — kick the tires — and if we like it, upgrade to the full version from within the app to take advantage of the full version. Developers only have to code and maintain one version of the app. As a user, I’m excited that I finally get to take the actual app out for a spin, rather than load the lite version, try, delete, either sync or lose my data, then download again. I think this will give developers a lot more flexibility in presenting a better initial user experience when downloading, previewing, and upgrading an app.

It’ll be interesting to see how this effects sales and app ratings in real life. In the past, I’ve noticed that the trial or lite version of an app typically gets lower ratings than its full-blown sibling. This is understandable because many more people are using the lite version to try an app out. If it doesn’t meet their needs, it gets deleted and gets a lower rating. I don’t think I’ve ever given five stars to a lite app that I was about to delete after trying. I wonder what will happen to app ratings when the group of tryers is merged with the group of buyers. I wonder how this will effect the usability of the App Store rating system when shopping for an app. This is something that Apple will need to work out.