I know a lot of people hate KDE because of the early 4.x builds. It has gotten a lot better now, and it's constantly getting even better.
If this is the case, he should take it for a spin. I find that it's the most customizable and user centric DE around.
There are a lot of settings you can tweak, probably too much for some, but I know each time I test Gnome/Unity/Xfce/Lxde/Cinnamon etc. I miss a lot of easily accessible settings.
The community is also great, there is a saying: KDE is the community, not the software.