I loved the KDE 3.x series, it felt like the future to me. It was _way_ ahead of both Windows and Mac at the time in terms of features and power.

KDE 4 was a dud. Too much of a radical make-over instead of iterating on what worked. Ugly. Very crashy. I'm not sure how close KDE 4 came to killing KDE altogether, but it must have been pretty close.

KDE 5 was a vast improvement over 4, going back to what made 3 so good. Earlier releases left a bit to be desired and still had a few stability issues. Later releases were pretty well refined. I switched (back) to KDE at this point, when I switched to Debian 12 (bookworm) at the same time.

KDE 6 is just a continuation of KDE 5, but using Qt 6 under the hood and defaulting to Wayland. It's very solid, fast, and just gets out of your way so you can do real work with it.