I use Extras-Devel to get some packages like, for example, mscim and anki. It is risky, but I pinned Extra-Testing for all software to prevent my system from upgrading to Extras-Devel.

I also use BackupMenu. Coincidentally, I needed to restore from back-up yesterday. A package made my system broken beyond my power to repair it. Again, Extras-Devel is risky, but some packages in it are really good.