I've finally joined here after using it a resource for quite a while. I have used Xfce for a few years. I also use KDE and haven't deserted it but find I use Xfce much of the time.
I first tried Xfce in Xubuntu about 4 or 5 years ago and wasn't happy with either the distro or desktop. I finally settled on Fedora and starting using Xfce when KDE 4 was released. I didn't stop using KDE but needed an environment that I could rely on so Xfce was added to the system. It has remained part of my system ever since.
I currently use Kororaa 16, a Fedora remix, with KDE and Xfce both are version 4.8!.
I like Xfce for its stability, reliability and performance.