I seem to think i had some ATI demo where there was some voice saying "blah blah blah, introducing blah blah blah technology blah blah blah ray-de-on" and if the ATI people pronounce it Ray-de-on or raid-eon, wouldn't that mean that that's the correct way to pronounce it? Seriously though, this argument has gone on long enough... it's not like it really matters. And it's not like we haven't already said all the possible ways it can be said.
I've always pronounced it Raid-On. I don't know why. Probably because I'm lazy and it's easier to say.