First of all, I'd like to thank Jonathan for his work. I have never used KUbuntu, but it has probably benefitted a lot of people.
But... I have always wondered why Ubuntu kept so many supported and unsupported variants around (Kubuntu and Xubuntu). If you want to target the end user and gain some foothold in the marketplace, you have to focus on making one approach perfect, rather than scattering focus over some subpar solutions (for the end user).
There are plenty of distributions for expert people that want to run Xfce, KDE, or fvwm, including Debian. But there is almost no distribution that focuses on just one environment, and makes it perfect for the 'average joe', like Apple did with OS X.