BIG difference in sound quality. I guess my room is a lot like fredk's...a concrete bunker (laughed out loud at this, never thought of my basement this way
) After I installed all the drywall in the room, the smallest sounds would echo like crazy. Even dropping a drillbit sounded thunderous.
Now, I hear no echos or muddiness at all in the theater (except for a litte bit of reverb coming from the untreated stairwell, but I don't think there is anything I can do about this). It is nice to be able to have a conversation in that room (no movie or music playing, of course) and not hear your voice echo at least two or three times.