Ubuntu GNOME 13.04 (Raring Ringtail) is the new kid of the block, and the impending release of the distribution on April 25 represents the first official version under Canonical's umbrella.
The Ubuntu GNOME developers have been rather shy and there isn't any real information about the operating system.
The only certainty is the fact that Ubuntu GNOME 13.04 will use GNOME 3.6 branch. This is mostly because the other Ubuntu flavors haven't upgraded to 3.8, as of yet.
Users will be able to upgrade to GNOME 3.8 by using an official PPA. Just enter the following commands in a terminal near you:
sudo add-apt-repository ppa:gnome3-team/gnome3
sudo apt-get update
sudo apt-get dist-upgrade
Ubuntu GNOME 13.04 will also feature UEFI support, it will be based on Linux kernel 3.8 (just like all the others), and will benefit from 9 months of support.
You can download Ubuntu GNOME 13.04 Beta 2 from Softpedia. When the final version is launched, you can just perform a simple system update.