Here's an interesting insight on the Ubuntu-marketing mail list where the competitors to ubuntu are reviewed.
Read it here at the list
If I were a newcomer with a windows legacy I would not give Kubuntu
live CD a second try, but go straight to pclos.
I think the excellence of K/Ubuntu would not be found until after
installation, nor the community nor many other of the approaches which
mean a rounded successful Kubuntu distro.
The desktop background in Kubuntu is unsophisticated and not pleasant
on the eye. The near symmetry is unattractive and the shades of blue
are also unattractive. These are fixed for Live CD users. Installs can
be expected to configure backgrounds easily of course if people are
forgiving enough to continue to install.