Gave this a try and BLEEEAARGHHH!!! Framerate went from 40-45 to just 2...
Well, I have to give credit where credit is due - the 1.0.47 update fixed that. Fake isn't quite as smooth as real fullscreen, but the performance drop is small (<5 fps) and Alt-Tabbing now seems to work OK.
Load/save times seem to have improved significantly too - about 20-25 seconds. So if anyone hasn't applied the update, I'd suggest they give it a go.
