To the OP:

the apps frpm nokia you can take as safe and use without any concern.
The apps in extras are almost completely safe, and you should be able to use them without trouble (there's about 90 of them.)
Apps still in testing should be treated with a little more caution. Check them out in the repository list first to see their karma and and serious issues which have been reported.
Apps in extras-devel should be treated with a lot of caution.

Hope that helps.