I have been using the K Desktop Environment (KDE) since the mascot was Kandalf, and Kandalf retired in 2002. In those days, my main distro had been Red Hat Linux, then Mandrake Linux, then, when Ubuntu made a Debian distro that didn't need magic incantations to install, Kubuntu.
When KDE came along, desktop environments for Linux were pretty basic - well, desktop environments in general were. Windows 95 and Mac OS 7, 8 and 9 were not a lot better. KDE had a lot more polish than the other DE's for Linux. When Ubuntu came out with Gnome as it's default DE, I gave it a go, but found it a bit basic.
KDE has been through a lot of growing pains. The change from version 3 to 4 was pretty painful, the development of Pulse Audio and Desktop search were all big transitions and why staying with the stable version is probably the better option. But it is still, in my opinion, the best DE available.