Most projectors operate best in very dark conditions. People don't, though.
What I ended up doing was to automate the lighting in my room, using dimmers and some software. A gentle fade down to darkness in front (where the screen is) and down to very dim light (where the door is, behind me) seems to work out well. At the end of the movie, the lights fade back up slowly. This turned out to be annoyingly expensive, but for me it was worth it. As mentioned above, sudden light transisitions are unpleasant.