I use XFCE.
It stays out of my way. I'm productive in it.
Unlike any of the current Tablet UIs for the 14 year old out there (UNITY, Gnome3 Shell, Windows 8 RT, Windows 8).
I just won't use them.
Even on my Android, I'm not using the those fancy "swipes" bullshit. Haptic feedback and a reasonable performing smartphone with a nice browser, gmail client, calendar client and a few others... I am set for most stuff.
I only have some games on it to tide time waiting for things.
There is also a reason I use Debian Sid. It just works biatches. If what I'm doing/using ends up having issues... I switch to something else just fine for the time being.
But this whole Tablet interface crap... just ain't gonna cut it for me ever.
Edit: Clarity on the "Tablet UIs for the 14 year old" vs "the 14 year old Tablet UIs" kinda not what I meant.