Back in 1998 I first tried Linux on my PC and tried the various desktop environments of the day including FVWM95, and they all sucked really, and my terminal foo wasn't so good back then. KDE 1.1 was what made Linux finally work for me as my primary OS. I could finally ditch Windows 95. I wasn't too thrilled about the single click thing but it didn't take too long for KDE to introduce optional double clicking. The other killer app on Linux for me at the time was the KDevelop IDE. It gave me a real path from VS on Windows 2000 to using Linux for all my development. I no longer use KDevelop, but I still use kdbg from time to time.
My uni's CS department had a bunch of Solaris labs running on x86 hardware, and CDE. I found a bunch of KDE binary tarballs for Solaris and ran it from my home directory and it was really nice. Other students saw that and started running it too. Eventually the Sysadmins installed it for everyone. I think it really did change how students looked at Unix. Later on as a sysadmin myself I oversaw the complete replacement of HPUX and Solaris with Linux, and we gave students their choice of Gnome 2 or KDE. Both were well liked by the students.