I have a Sammy HLN507W since last July. Neither the wife, nor I, nor any visitors, have ever seen a rainbow. I checked the AVS forum about rainbows rather extensively last fall and the best advice I saw was that if you see them so be it. If you don't, good. If you don't and you try real hard and finally see one, you will then see them all the time.
The wife and I chose the DLP/RP over LCD/RP because the DLP has a much wider effective viewing angle, has brighter color display (no soft wash out look), has better black definition (no crushed blacks), and deals with a lighted room much better (less screen glare and less color washout). These were important aspects as this DTV is in our family room adjacent to our nook and our seating positions are both at an angle to the screen. All that after we originally set out to buy a Sony LCD/RP and never owned anything from Samsung.
I love this DTV, but the color wheel noise is a problem. My high frequency hearing was left on an Army machine gun range many years ago, but the wife has super-sensitive hearing. She said the thing started screeching at startup last October. The service tech agreed with her and replaced the color wheel. Now it is screeching at cold startup again and even I can hear it. So, we will be calling service shortly. We got a 5 year service warranty on the Sammy, so unless they come up with a better color wheel, I guess we will replace it twice a year until 2008, then dump the set.
The other problem was noted by the service tech last fall when he opened up the set. These things really collect a lot of dust. They are particularly bad if you humidify your forced air heating in winter like many of up in Metro-Denver do. The lamp heat cause the minerals in the water to precipatate out all over the electronics in the path of the cooling ventilation.
It's a shame because this set delivers awesome HDTV and, with good wiring and a good power center, very good SDTV from DBS or OTA digital or analog signals. Read the manual carefully. A lot of the enhancement electronics aren't active when you are using a DVI input, as I do. But, I don't really see the need for any more enhancement.