XFCE is quite a surprise I think. It's definitely making a big step with 4.4 and it looks like Gnome is becoming redundant as XFCE does just about everything Gnome does, using the same toolkit yet is lighter weight.
ya but it is not exactly there yet but maybe another year it will be but that is just my estimate. even then more people will probably use gnome than XFCE because of ubuntu's preference.
KDE for use on a desktop system all of the way. Gnomes who talk about their desktop being lighter weight and less Windows like than KDE don't know what they're talking about.
now lets give credit where it is due, gnome is lighter weight than kde but then again being lighter weight means less features so it is a trade that some people like and others dont.
i have heard the 'gnome is less like windows than kde' thing a lot and i dont really know why. you hear that everywhere on hte net from every guy and his mother and none of them really can say in what ways kde is more like windows than gnome. since i dont get that arguement it is not usful in my decisions.
basically the way i see it is kde has more flexibility and gnome is more stable.