I'm in the same situation. I prefer Debian in almost every way, but Ubuntu gives me one *very* valuable thing: a 6 month release cycle. This lets me run much newer software than Debian stable, yet breakages can only happen at fixed times - release upgrades - and those I can do when I have time to handle breakage. (I also enjoy the free PPA infrastructure, but it's no dealbreaker for me).
Debian is wonderful, but Ubuntu really hits the sweet spot for me as a *non-rolling* distro with a perfect release cycle.
I'm glad I can stay with Kubuntu a while longer, thanks to such reassuring statements and great work by Riddell and the other Kubuntu folks.