KDE is very easy to use 14 year old girl have no problems with it (also experience from family ).Both Gnome and KDE are usable by an experienced user. However, Gnome is also usable by an inexperienced user, while KDE tends to be too confusing (judging from experiements on my immediate family).
K3b, Amarok, Konqueror, Kate, Octave and few more. However, it depends on taste. I used Brasero before instead of K3b (when there was only qt3 libs version) and I like it. Of course, I use Open Office and Firefox, because it's hard to find good alternatives right now.KDE is not bad, but it doesn't really offer anything Gnome doesn't already do better. Name any app! Chances are you'll find a better alternative built on the Gnome stack (Firefox, Banshee, Brasero, Gnome Do, OpenOffice, Chromium, ...)