If I could find a way to separate image window and tool box it would be perfect. I've been using two displays -specifically for graphics and video editing because that is how god wants it ro be! No discussion with the heretics of the third incarnation!- since forever and I hope GIMP has not gone the GNOME3 way of being useless on multiscreen environments.
I am anything but a GIMP hater. I've been using GIMP for anything Inkscape can't do for more than 25 years. Nevertheless, I didn't see "Single-Window Mode" even though I had the "Window" menu open at least three times, as well as "Preferences". I wonder, why it wouldn't just import these standard prefs from 2.x...