Treating the ceiling and floor, who else has had great results?

Two areas of the room often neglected by audiophiles IMHO is the ceiling and floor.  We focus so much on first reflections we forget about overall energy left in a room after the speaker has stopped.

I've had excellent luck with treating the ceiling, especially for home theater applications, and this was before Atmos.  The area behind the speakers near the floor often hides noise and distortion which we didn't know we were hearing.  Throw a blanket over there and listen for yourself.

Who else has gone through the trouble of treating their ceiling?