Comment 35 for bug 742544

@Andrea:
It seems that unity ignores the primary monitor setting in some situations.
Unity version: 4.20.0-0ubuntu2
Set-up:
right monitor, 22" Dell monitor no rotation, primary
left monitor, 19" Dell monitor, left rotation, not primary

Unity launcher still shows up on the left monitor (which I use only to display documentations and stuff
in a portrait-wise orientation). I believe this setup to be quite common.
I'm attaching a screenshot wich summarizes all the infos:

in .config/monitor.xml the primary monitor is set-up correctly
in the display panel, the black title bar is set on the right monitor
on the desktop, the launcher shows up on the leftmost one.

Note that Primary is also set-up correctly in Xorg.conf and lightdm shows-up
correctly on the right monitor.