I've watched movies in the dark as far back as the 80's. Even when I bought my plasma in 2001 I viewed movies in the dark, for the immersion and for the picture quality (no glare).
My projection-based home theater continued that theme. It's on the main floor of our house, used to be our living room, so it couldn't look like a cave during the day. My solution was to create decor that was very non-reflective for the most part - the ceiling is built down using a dark brown felt material stretched over a bulk-head. This provides both acoustic and light absorption:
I did a dark non-reflective chocolate shag rug (deep pile keeps it non-reflective), and a dark brown sofa. I kept the walls light so that by day they would reflect sun from the bay windows and keep things bright and cheery. But when when the system is turned on to watch a movie, the black-out blinds automatically drop to seal off light from the windows. I then have black velvet curtains that I can pull around the room, sealing it as a "black, non-reflective box."
That in itself was enough to make sure I was getting all the great contrast I paid for with the JVC projectors I use. But I found the more of the room I could remove from my vision, the more immersive and dimensional the image looked. So I had black velvet covers made for my L/C/R speakers, making them disappear from view with the lights out. I also have a black velvet "blanket" I can throw on the dark rug in front of the screen, when I want the ground to totally disappear. Recently, I even added another black velvet curtain, when I want to go "all out" and make the room disappear. Even though the dark brown felt ceiling is very dark, compared to the truly pitch black Fidelio velvet used for my masking system, speakers etc, it is more visible during movies. So I added yet another black velvet curtain a while back. The curtain stacks to one side of my screen and is on a rail over the screen. I pull it across the screen wall, then it has loops sewn into both sides which are hooked on to hooks on the drop down ceiling, so the ceiling becomes covered in pitch black velvet.
This really makes virtually everything disappear but the movie, even in bright scenes, and when you remove other visual cues, leaving only those from the projected image, the sense of depth into scenes can be amazing.