I guess I would file this under the category of "unnecessary but nice idea". It would be nice to have some sort of support for multi-monitor setups, that way if I wanted to check something like my map or inventory or other miscellaneous things without it intruding on my screen space I could just click and drag said items over to my side screen.
Like I said, totally unnecessary, but it would be pretty nice to have.
EDIT: Since I'm silly and didn't check page two, I found this thread covering the same topic