While KDE Plasma is far more powerful and flexible than GNOME Shell, I love the design simplicity of GNOME.
I decided to have the best of both worlds by making my Plasma installation look very similar to GNOME.
-Plasma theme: Caledonia
-KDE style: QtCurve modified to look like GTK theme FlatStudioLight
-KWin deco: Customized QtCurve
The icon in the top left is from the Gnome Shell Faience theme