MC 11 worked fine with multiple displays. I had video set to always play back full screen on monitor 2, and it would do that while still leaving my main MC window on monitor 1 for me to work with. With MC12, I have set the same options as MC11 (run video full screen on monitor 2) - but now instead of using a second window it moves the main window over to monitor 2 and leaves it there.
Correct. The "unified" display view means that the UI moves with the "full screen view". This is the reason for the Detached Display, so that you
can still get the same functionality. The Detached Display will remember it's size and position (including which monitor it was on and whether it was full-screen or not last time) when you "re-attach it". So, to always have it running full-screen on the second monitor...
Set your
Display Settings --> Full Screen --> Monitor setting to
Nearest Monitor (the default). Unless you want the UI to move to a specific monitor when you go full screen this is what you'll need to set, and it's really what most people should use now. Start a video or something playing and detach the display. Move it to the second monitor and full-screen it (double click). Now,
don't un-full screen it to bring it back but instead either: 1) click in the Playing Now window on the main MC UI (where it says "click here to bring it back", or 2) right click in the full screen display and choose "reattach display". You should have your video back in the main MC UI.
Now, try it again. Start a different video, right click and choose Detach Display. It should automatically go full screen on your second monitor. It goes where-ever you last put it, however you last put it, when you last "reattached" it.
As I just posted over here, the new MC12 multi-monitor stuff is actually quite a bit more powerful than MC11's was. It does take some getting used to, but for people who have never used MC at all before (so aren't used the the somewhat weird "choose your full-screen monitor ahead of time" way that MC11 worked) I think it's actually quite a bit more intuitive. Just leave that Full Screen setting alone, put it where you want it, and it remembers to go there next time. Simple.