I joined as a user at one point during the kde3 days, powerful apps like Amarok 1.4, k3b and konqueror with all kinds of crazy kio-slaves were the ones that really gave me pause on the boot screen and kept tipping me over towards mandrake instead of WinXP ("why can't it be that simple and as well integrated, why do I need so many ad-hoc shareware to do every basic thing like burning/ripping CDs, mounting ISOs, transcoding audio, sending it to my MP3 player").

The KDE4 days were rough, by then I had jumped over to fedora, and that one didn't shy away from shipping very early and unstable versions of it. That had me hopping for alternative DEs, I seriously tried several (and stuck for a while with some) of the minimalistic ones (enlightenment, XFCE, ...) and quickly ended up depending on either KWin, and/or some battery/networking/disks applet from plasma, or configuring something via systemsettings. The plasma desktop itself is fine (I don't mind it so much, I'm not crazy about shell theming and customisations, I do love my global menu on top, though), but what sells KDE for me is all the clever ancillary stuff that makes it "smart and usable" (dealing with Bluetooth, network setup, local and remote drives, audio output, ...), that's where the "environment" metaphor kicks in and elevates the experience above that of a "desktop shell".