Swampthing- Yeah, seven years into the "new" studio and it still feels great to show up in the morning to go to work. The interior walls off all the studios (video rooms included) are a sandwich of 5/8" sheetrock, 1/2" celotex soundboard, 3/4" MDF, and 1/2" sheetrock. All seems are taped and mudded and all seems are staggered so none line up with any others. The great thing about MDF (aside from its density and sound-stopping properties) is that wall treatments can be located anywhere on the walls or ceilings- no need to find a stud though all that mass. You can put a screw in anywhere. I hadn't heard anything regarding poisonous off-gassing of MDF, or I might have spend more time researching the stuff. It is a pretty weird material. We do have very good HVAC that circulates new air into the rooms completely every minute and a half or so, so if there is a problem, at least its ventilated well.