do what i have decided to do,
read about the app you want to test
find out if it installs to opt before installing b/c as a noob i dont want to run into memory problem.
once your satisfied that what you want to test you can cope with, install it then disable repo so not to upgrade stable apps from extras with versions in extras-devel or extras-testing by mistake.
take note of apps you are testing so you can check for updates from less stable repos now and again without having to get all updates from repos hosting unstable software.