I remember having this conversation, with you in line with my thoughts, a few years ago! You went from what, seleco, to a DILA, or something like that?
Two things I would say, and agree with what others have said.
For those who say it is blown out of proportion, you are speaking from your own viewpoint. To anyone who is bothered by them, it can be VERY proportional indeed.
Secondly, there is CLEARLY a link between brightness/contrast and rainbows.
I was at a store watching a Sim2 a year or so ago. It had a 4x or 5x colour wheel. When ambient light was on, in the background and sides of me, (not hitting the screen directly), I saw very few rainbows. I was watching Gladiator on an 80" screen.
However, when the guy turned off the lights completely, there they were, as bright and noticeable as ever. I am not certain if it is contrast, or brightness that is doing it, but I would warn everyone that if you are considering a DLP, make sure you test it in similar environments that you will be in your own home. My room is completely light controlled. It is a cave, and based on my experience, I know this would have an affect on rainbow visibility.
All in all, lets keep this simple. Those of you who own a DLP and don't see rainbows. You are fortunate. However, there is no need to claim that somethign is out of proportion, because it does not affect you, or yoru 20 friends. This thread is just to keep everyone informed about the phenomenon. Clearly, we dont' have one for screen door effect of FPN, or whatnot, because these are readily visible to everyone who has good eyesight. Rainbows, on the other hand, involve so much more than just your visual acquity.
I am certain that the thread creator had no intention to put anyone on the defensive, or make you justify your purchase. Indeed, if you don't see rainbows, you shouldn't need to justify anything in the first place.