KDE 3.5 was fine. KDE 4 is not.
I use Ubuntu 9.04. I heard too many bad things about the 10.04 LTS version, so I'm sticking with 9.04 for as long as they support it.
I recently realised my xD-card reader doesn't work. But everything else does, which is half the battle with Linux.
It does some funny things-like wiping menu.1st after a kernel update from the official repo, even when I select it not to touch menu.1st. It boots and shuts down as fast as Win 7 ( I dual boot).
Not sure if its gnome or the linux task scheduler or the fact that the GUI is just dressing on top of the command line she, but the GUI does have an annoying "stickyness" and "delay" about it.
It serves its purpose as a comms and media viewing OS, and video encoding machine. Nothing fun about using it though.