My system is in a dedicated room.
I never listen to it without eyes closed and seated in the sweet spot.
It's never used for background listening, the other two systems are for that.
Yes, it definitely makes a difference.
A free tweak revisited
I am absolutely positive that this subject has been discussed before, but last night as I was listening I was reflecting on how big a difference (for me) turning the lights off and (probably redundantly) closing my eyes makes. My listening room is a quite near field environment, but with the lights off/eyes shut I hear the illusion of a sound stage wider than the boundaries of the room with height and some depth. (However, the sound stage I get is not as deep as it is wide.) Opening my eyes and looking at the speakers so close to me is kind of like sticking a pin in the balloon.