The thing that keeps me on Linux (mostly), is the ability to use alt+drag (I actually re-bind this to Win+drag) to move and resize windows without having to move my mouse to the title bar, or to the thin edges of the windows.
I can just use alt+left drag to move my window, a large target, anywhere I want it to, and likewise to resize it.
It's really annoying for me when I have to use a Windows VM (for example), and not be able to do this.
If you use VMware Player (and/or presumably Workstation) in "Unity" mode, you can alt-left drag to move and resize the virtualized-Windows-windows. Sometimes it gets a little wonky, but it works great 95% of the time.
I'm constantly missing this when I work on an OS X machine. Somehow, I end up with the window titles offscreen and just get momentarily stumped when I want to move it again.
I can just use alt+left drag to move my window, a large target, anywhere I want it to, and likewise to resize it.
It's really annoying for me when I have to use a Windows VM (for example), and not be able to do this.