gNatty is an Ubuntu remaster based on Ubuntu 11.04 which includes GNOME 3.0 packages via the UGR (Ubuntu GNOME Remix) project as well as the ricotz/testing PPA.
The customization only includes GNOME 3, so everything else is similar to Ubuntu 11.04. An important aspect of gNatty is that you can run both GNOME Shell and Unity (3D) as long as your computer supports them, by simply selecting one of the two in the GDM login screen as you can see in the short video below (gNatty running in VirtualBox):
(For more videos, subscribed to the WebUpd8 YouTube channel)
gNatty is not for everybody so be careful! An update may break it so only install it if you know what you are doing. For this reason, Charles Bowman (who is behind gNatty) recommends you disable the ricotz/testing PPA immediately after installation!
The gNatty torrent comes with lots of extensions and GTK / GNOME Shell / icon themes, but these are not installed by default so you must manually install them.
As you can see in the above video, installing a GTK2+GTK3 theme is a must. Zukitwo as well as others are available in the torrent so use GNOME Tweak Tool (it's in the PPAs that gNatty comes with so install it via Synaptic or Ubuntu Software Center) to apply one of those themes
Selecting "Install" when booting the Live CD will fail you must select "Try Ubuntu without installing".
Once you boot the Live CD, there's no icon on the desktop (because desktop icons are disabled for Nautilus 3.x by default). So you'll have to select System > Administration > Install Ubuntu 11.04 to start the installation process.
For more info, support and download links, see the gNatty post @ Ubunuforums (the latest version was released on June 22).