Kubuntu is part of the Ubuntu project and uses the same underlying system. It is possible to run both the KDE desktop (kubuntu-desktop) as well as the Gnome desktop (ubuntu-desktop) interchangeably on the same machine. Every package in Kubuntu shares the same repositories as Ubuntu. It is released regularly on the same schedule as Ubuntu.
What's new in version 12.10 (Quantal Quetzal)
Version 12.10 (Quantal Quetzal) has added two world class apps from KDE's creativity suite, added a Wacom configuration tool for those with tablet input devices, and replaced the login manager with LightDM.