for what it's worth, when I first got my jvc, x35 I had white ceiling and light tan colored walls. with the lights off I thought it looked FANTASTIC and was a huge upgrade over what I'd seen before.
the ability of the jvc did encourage me to take the steps to start making my room darker and better at absorbing light, but I don't feel it was wasted before that. think of it like driving a 4wd vehicle on-road. the extra capability kinda makes you want to take it off-road, but it doesn't really subtract from it's on-road performance.
I actually read your post, and see that you said you'd be using it 'mostly for movies' and even with white walls, these projectors will be a significant upgrade over a cheaper(1070) projector when the lights are off and you're watching a movie. when you turn the lights on a bit for sports, sure, you're going to lose some quality, and difference between these projectors and something cheap won't be as obvious, but that's not the only way it's being used, so it's not a waste to buy a nice projector.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1130K, 7.1/5.1.2 audio
Sources: HTPC(Enby), PS3, XBOX360, Wii
Control: Harmony One