I just tried out the Ubuntu and Kubuntu 9.04 betas earlier today, and I think my interest in both GNOME and KDE is just about worn out.
Both are really quite bloated. I've been on Debian and KDE 3 for years, but I think I'll be switching to a stand-alone window manager like fluxbox, or maybe Xfce, the next time I have to upgrade.
GNOME on Ubuntu felt as sluggish and amateurish as ever. No amount of new themes and rehashed icons can improve GNOME. As a KDE user I was looking forward to KDE 4.2 but christ, it's so damn cluttered. I think they've actually added more clutter since 3.5, not taken it away. Every damn UI element flickers and flashes with a mouseover effect as you move around; some kind of indexing service is hitting the disk in the background; there's a plethora of desktop views or applets or whatever they're called, none of which I'm interested in; there's a new K menu that looks like it was a reject from Windows XP, and which takes several clicks to hunt around for what you're looking for; the default widget theme has super thick borders, even the pull down menus have thick borders around the menu items. The whole thing is just over-cooked. I couldn't make sense of it, frankly.
Sure, I could turn off or tweak most of that junk. But I think what I saw today is what happens when you try to copy Windows and Mac too closely. You end up copying the bad as well as the good. You inherit the same limitations and the same performance standards. It's a poor form of competition, and I despair at how much programmer effort must have gone into creating all this bloated mimicry.
Having said that, I only just scratched the surface. I know how good Qt 4 is, and I'm sure developing apps with the KDE4 framework is much nicer than KDE3. It's just that the result on the desktop (both of them) is a bit of a let down.