After seeing the latest "innovations" both Unity and Gnome 3 brought to the table, I made a switch to Arch Linux with OpenBox, permanently.
IMHO both Unity and Gnome 3 are doing a great disservice to Linux
"Optimized for tablets..." What tablets? Where are the Linux tablets? All I see is out there are iPads and Androids, with Microsoft joining the fray with Windows 8 soon.
What will probably end up happening is what we've already seen with Linux on desktops: Ubuntu and possibly some other tablet-optimized distro will try to sign up a hardware vendor (say, Dell, since they seem to be somewhat friendly to the idea)....and fail, due to the market realities (aka. other OS vendors with deep pockets and deeper market penetration will eat their lunch)
Then they will try to position themselves as an alternative OS on somebody else's tablet (be it Android or Win8), with minuscule uptake (hobbyists and enthusiasts) - mostly because they will have too many rough edges being not fully optimized to run on proprietary hardware.
In the meantime the majority of Linux laptop/desktop users will struggle with the tablet-optimized UI ....or switch to something more usable, maybe even go back to Windows.