used it last night. darkadapted worked great on my iMac, very easy, no quality loss. in the progress i also had the idea to reduce the overall brightness of the screen, which worked great too. on the pc, not so much (a sony laptop, windows xp, with a dell external lcd monitor). i suspect part of the ease was due to imac's integrated operating system/hardware/monitor, i realized in fooling with it that monitors typically(and mine did) have their own independent color settings that would need to be adjusted. i didn't think to try it with just the laptop screen, but that would probably help. after messing with the monitor coloration i did get better results using darkadapted, though i can't say the picture adjusted to all red anywhere near as cleanly as on the mac.
as far as the effects, i felt myself getting pretty tired much earlier than normal (im normally on the computer until about 1230, in bed at 130, and read for a bit) and wound up dragging myself straight to bed at 9. i had shut off all the lights in the house and closed the curtains at sunset. maybe it was all psychological, though.