Ubuntu-based, independent developers. Commercial support available. Pkg mgr Muon Discover, plus a plain graphical pkg mgr. Codecs/proprietaries available; "Additional Drivers" widgit. Social networking app built into desktop. Has 'Kubuntu Updates' and 'Backports' PPAs.
Changes at Ubuntu will affect Kubuntu; possible rolling release in Ubuntu, Cannonical might be dropping support for KDE, for development, and discriminating against non-Cannonical (profitable) releases and communities. Offers btrfs (causes error).
Check UltimateEdition repos for kubuntu (compatible with ubuntu).
o Distrowatch: http://distrowatch.com/table.php?distribution=kubuntu
o Ask.com: http://www.ask.com/wiki/Kubuntu?qsrc=3044
o home: http://www.kubuntu.org/