When I find an new application, I often wonder if it is worth installing - especially if it has to install a bunch of dependencies along with it. If you just want to have a feel of the application before installing it, Ubuntu 11.04 has a new feature in the Software Center, called Test Drive (not to be confused with TestDrive which runs the latest development snapshot of Ubuntu in a virtual machine), which runs the application in the cloud and allows users to use try it out.
To use Test Drive, you need to be running Ubuntu 11.04 and install a package called qtnx.
$ sudo apt-get install qtnx
After installation, you should see Test Drive under the screenshot in the Software Center.
The concept of having applications running in the cloud for users to test is nothing new. Recently Amazon included it in its Android app store. Incidentally that feature was also called Test Drive. And if you remember, Ubuntu's educational derivative - Edubuntu - also introduced something like this when Edubuntu 10.10 was released. The service called Edubuntu WebLive allowed users to try out Edubuntu without installing or downloading the ISO.
However running separate instances of applications in the cloud for users to test it requires considerable computing resources. So, Amazon removed its Test Drive when the app store was officially launched and Edubuntu's WebLive was limited to only two hours per person.
Similarly, Ubuntu's Test Drive is also quite limited right now. Test Drive will be available for only the top 30 applications. While the decision to restrict Test Drive to only a limited number of applications is understandable, I think if they restrict it to the top 30 applications it kind of defeats the purpose Test Drive. Most of the applications in the top 30 are probably known to most users anyway.