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

GIK absorbers on ceiling and side walls along with a good thick cut pile wool rug with pad. Vicoustic combination absorber/diffusers in the front corners, on the front wall, and on the side walls. In the middle of the front wall is a large Vicoustics wooden diffuser ensemble. There are also Vicoustic diffusers on the ceiling. Behind the listening position is another mix of absorption and diffusion devices. Probably 50/50 absorption/diffusion overall.

My recollection is that you want to treat roughly 30% to 40% of the room's surfaces. 

This may not be an option for some, but Armstrong makes suspended acoustic ceiling tiles. I used these in my sound room and they worked wonderfully to mitigate an upper midrange glare. They are also inexpensive and look good. 

Ceiling: completely covered with 14” of rock wool, which is covered with fire-resistant burlap

Floor: mostly covered with Moroccan and jute rugs.

Walls: see ceiling, but 5”.

I would say that 75% of the room surface is deadened. The room is about 25-30 db. It is semi-anechoic.

I was able to include a dedicated listening room when I designed  and built my home. I installed a diffuser at the first reflection on the ceiling as well as the walls. The walls also have absorption at the second reflection. The floor is carpeted and has one joist space at the first reflection that is grated and filled with fiberglass insulation. The music sounds amazing.

Large room with high ceilings a wood floor here. I fitted a 10’x14’ area rug with 2 layers of carpet padding underneath between the speakers and my listening position. Before and after REW waterfall plots show a marked reduction in early reflections from the floor beginning around 1k or so on up.