First off there is no upgrade path and instead you are forced to do a full reinstall. (slackware 1.0?)
Once I reinstalled on my main desktop where I was quite happy with 11, the gnome-shell kept respawning. (radeon video)
Forcing an upgrade to drivers did not help as images were completely corrupt on restart.
Then on the work laptop where 11 has worked fantastically 12 hangs during the boot.
So, I can't say I'm a big fan of this release.
Seriously guys work out the non-existent upgrade path.