Re: [GNOME] gnome-shell/mutter/clutter unusably SLOW: 173xx
This is just a performance problem on new (relative to the GPUs 173.14.* supports) desktop environments, right? The legacy drivers get support for newer kernels and X servers (though I'll admit I'm behind on adding support for xserver 1.11), but not things like performance improvements or support for new features.
I'll see if I can give it a try on one of my legacy GPUs, when I get a chance, to see if there's anything obviously wrong. It's likely that mutter/gnome-shell is just hitting a rendering path that was not very well optimized back in the 173.* days, so don't get your hopes up.