After few days from the last Beta version, and few days before the official release scheduled for the end of April, Canonical released the Release Candidate of both Ubuntu and Kubuntu.
For Ubuntu the major changes will be GNOME 2.22 and Firefox 3 Beta 5 while Kubuntu will have the benefit of having two parallel versions: the official one with KDE 3.5.9 and the “KDE 4 Remix” with KDE 4.0.3.
In the programming world, a Release Candidate is an intermediate version of a software (or a whole Linux distribution in this case) that is released between the Beta version and the official release to the public; normally it should not contain any major bug (since bug hunting is the scope of the Beta version), but nevertheless it is released as “last check before release”.
Ubuntu’s Home Page: http://www.ubuntu.com/;
Ubuntu 8.04 announcement:http://www.ubuntu.com/testing/804rc;
Kubuntu’s Home Page: http://www.kubuntu.org/;
Kubuntu 8.04 announcement: https://wiki.kubuntu.org/HardyHeron/RC/Kubuntu.