I remember it well. I was a heavy KDE user through most of the aughts until I got an iBook. It was awesome. Very tweakable. Thoughtful apps, if a little instable in a few places.
It's still bewilders me how KDE turned into... this Plasma thing. Did the entire team behind KDE just walk out at some point?
For what it's worth, I think the current KDE Plasma is quite evenly competing for the nicest desktop environment around (including the proprietary ones in functionality and looks -- polish is behind due to obvious mismatch in development manpower).
The whole "desktop widget / workspace" thing in KDE4 was a complete waste of time, like the "tabletization" that followed. It felt like they were chasing fashion, cranking out slow and half-broken me-too implementations of very debatable concepts. That's when they lost any hope of ever challenging in the mainstream market.
They're also cursed by the typical open-source churn, where they replace battle-tested programs with unstable "new shiny" just because nobody wants to maintain old code.
I left when I didn't like the direction any more, somewhere after 3. Nothing against the team, almost everyone was absolutely brilliant, it just wasn't going where I wanted it to.
It's still bewilders me how KDE turned into... this Plasma thing. Did the entire team behind KDE just walk out at some point?