Anyone know where the Gnome 3.12 ppa is? Is this it?
Of course that is all just a guess. If you want new versions quickly then switch to Arch. Just try it in a virtual machine or spare machine as there is a learning curve for Debian users.
In the mean time I am happy enough with 3.8 on testing. I have tried the newer versions through experimental and Arch, but in the end Gnome Shell does not change that much and newer versions have less extensions available as it takes a while for extension authors to catch up. We have to go through the systemd change and then Wayland. My testing "just works" and that is good.
However, the mailing list archive's are dead (chromium says it redirects too much), blogs are not that alive and the last forum announcement was last year... hmmm :/
Best thing about GNOME 3.12 is the improved Wayland support, which unfortunately is still not done.