Among many of the new changes is the adaptation of Gnome3. But before anyone gets too exited :) Gnome shell is not included in the CD but it will be supported in the official repositories. So after downloading the Oneiric Ocelot 11.10 Alpha 1, if you wanted to install Gnome 3, then you don't have to rely on the previous PPA... just open your Terminal and enter...
sudo apt-get install gnome-shellThat should do it. But remember, this is an Alpha release... so there could/will be issues.
Although we were confirmed of the lightDM which is gonna replace the current log-in manager GDM, yet according to Canonical it's not presented in 11.10 Alpha 1, for the obvious reason of the OS being so "alpha". But we should see lightDM in the future Alpha versions nonetheless.
Few other changes...
*. Now Oneiric Ocelot comes with Firefox 5 Alpha 1, Nautilus 3.0, Totem 3.0, LibreOffice 3.3.2, Compiz 0.9.4, Banshee is also updated to the latest version 2.1.0, Gwibber 22.214.171.124 and the Linux Kernel 2.6.39-3 are among the many apps that have received updates.
Simultaneously Xubuntu, Kubuntu, etc Alpha versions are also available. You can get more information (concerning downloading, etc) from this official Ubuntu Oneiric Ocelot release page.
Remember, it's still at the Alpha 1 stage, so use it at your own risk :).