You'll find the most recent, and probably the largest selection of packages in our testing repo. Unfortunately not enough people pipe up and let us know if they work good or not. So they just sit. And in some cases, they get outdated. You'll get mixed opinions from users whether enabling testing is safe. Just keep in mind the packages need YOU (and others) to test
Honestly I've seen very few packages that blatantly mess things up. Most often the worst you'll find is deps don't work themselves out properly, or a menu entry doesn't work.