Tried this theory with my LP340 which is usually connected to a PAL Dvd player, 50hz...
Hooked up PC on the VGA port and chose 75hz on the vga card - everytime I switch between the two I can hear the 'whining noise' - the colorwheel - speed up or slow down.
So yes, rainbow might be less of an issue on higher frequencies.
Ah, and those that hate HTPC's, has anyone ever considered this: Instead of using a PC to control the players etc... Build a custom PC with a capture card and dTV - just use the PC as a deinterlacer, and keep using the DVD player & tuner/video whatever, with their outputs going to the pc. Set the PC up for native resolution out at 75hz and hey presto... If you're handy you can make it boot into dtv automatically - no more keyboard, mouse, etc... just a cheap external scaler ;-)