Ditto what the other guys have said. I've not seen flat paint in a HT in person, but almost went with it for mine.
I went with a semigloss dark brown (chocolate) paint on all walls and ceiling. There is little to no reflection during projector use; i.e., I have not been made to wonder whether I should have gone with the flat. Plus, when the lights are up, it looks snazzier, to me.
CV, since you asked in another thread, I am tempted to one day tell the saga of the construction of Navajome Theater (formerly Stately Swing Manor Imperial Armchair Theatre), but I'm thinking that if it hasn't happened yet in my 1.5 years on the boards, that ship may have sailed. And taken my digital camera with it, apparently.
