I mentioned this on the edevelop mailing list. I will copy and paste much of what I said there, as it is basically the same. Rather than use slides, I have a video of a presentation that shows the issues first hand.
Here is a link to the presentation
You can see the issue with E at 1:25:00 roughly. Does cover some KDE stuff for a bit, but not bad to see.
E seems to be remembering settings for external display and at times applying them when not wanted. At my desk, when I plug in my laptop to external monitor. I have it set to keep that off. I use a script I click on a icon on my desktop to toggle the displays. Turn off laptop, turn on external. This works fine except E does spit out some error every time, but works fine.
Now on occasion I plug my laptop in, and wake it up from sleep and it has the external monitor on, and internal off. When it was not using an external at first. Seems to handle "hot" plugging when logged in better than when logged out, and doing your first log in with new external display attached.
In the case of my presentation. It would not activate the external monitor. When it did, it changed the resolution of BOTH my laptop display and the external to the lowest. When they were both capable of the highest, 1920x1080.
In this situation what I was expecting, like I got with KDE/Kwin. With a new external monitor connected. When first logging into E, both displays should be active, and at their highest resolution. The only time a display should be off. Is when it is the exact display that was connected before.
At my desktop I have it set to be off when plugged in. But if I plug in any other monitor, it should be activated. Ideally settings per monitor rather than globally. Or something along those lines. If monitors had UUID it would be great. I think things are limited to Vendor/Make/Model. Which does not help if using 2 of the same displays in different configurations.
Either way I expected E to have both displays activated. In the case where that does not happen. When I do activate and external display, it should not effect the resolution of the primary display. When it does activate the external. That should be at its highest resolution vs lowest.