I have used the 3 ubuntu variants, ubuntu, xubuntu, and kubuntu.
I finally settled with Kubuntu (KDE4) after using ubuntu for a while. WUBI installed, since my laptop is XP preloaded. i use XP over anything on linux that gives me headache
Anyway, what i like about KDE..
-i like the plasma desktop, modern look with default theme, widgets are nice
the KDE environment is tightly integrated
-Dolphin is much much usable than Nautilus, especially when you're used to windows. Nautilus is somewhat dangerous to use, you are not warned if you delete a file, it goes to trash immediately when you press del. this is a deal breaker for me.
-the "Start" menu is very easy to use, i use the search box a lot.. it's a time saver, and the menu is well organized ( XP doesnt have this only Vista/7 )
-theres a default shortcut to bring up a basic process manager, just press Ctrl-esc, but i don't know with ubuntu
however, Adding applications in ubuntu is much better than kubuntu
but as long as you have installed all what you need, (Firefox--defacto browser, Chrome--my modern browser, Opera--mail checker, XBMC-media center) it pretty a good environment to use..