Ubuntu 13.04 has been officially released today as scheduled, with the codename "Raring Ringtail." It is the 18th major version of the Ubuntu OS and will be supported for a period of 9 months.
Versions included in Ubuntu 13.04: Desktop Edition, Server Edition, Cloud Server Edition, Netboot, Ubuntu Core, Ubuntu Studio, Edubuntu, Kubuntu, Xubuntu, Lubuntu, Ubuntu-GNOME, and the Chinese Edition Ubuntu Kylin.
Updated components in Ubuntu 13.04:
Linux kernel 3.8.8;
Unity 3D interface 7;
Upstart 1.8;
LibreOffice 4.0;
CUPS 1.6.2 and cups-filters 1.0.34;
Python 3.3;
X.Org 7.7;
Xorg Server 1.13.3;
Mesa 9.1.1;
GCC 4.7.3 toolchain;
Compiz Fusion 0.9.9;
Key features of Ubuntu 13.04:
GNOME Edition: This is the first time that the Ubuntu desktop edition fully relies on the GNOME desktop environment;
Chinese Edition: Ubuntu Kylin, which was jointly developed by Canonical and China;
Unity 7 enhances the desktop experience;
Simplified software updater;
Redesigned file manager, still using Nautilus but updated to version 3.6.3;
Built-in latest office suite LibreOffice 4.0;
Integrated with Twitter, Facebook, ownCloud, Windows Live (SkyDrive), Google, Yahoo!, Flickr, and other popular social networks;
Equipped with the latest browser Firefox 20 and email client Thunderbird 17.0.5;
13 beautiful wallpapers;
Upstart User Sessions technology preview, allowing Upstart to monitor user desktop sessions;
Other minor changes.
Official download page: http://releases.ubuntu.com/13.04/