Firecracker,
If you check out my virtual system you can see how the new GIK Tri-traps integrate into a room in an aesthetic way. These use heavy mineral wool and are broadband absorbers (effective down to 100Hz with a tiny little bit of absorption even at 50 Hz).
As long as you have something broadly absorptive and with a density of 3 pounds per cubic foot or more (foam, fibreglass, mineral wool) then you can get some nice results with decent coverage. I believe that controlling rear wall (behind your listening position) reverberation is the most important use of these products.
As others have stated above a reflective room is pleasant and a dead room is dull and lifeless....which suggests that one should avoid heavy acoustic treatement in front of the listener.
Behind the listener is another matter.....anything reflecting from behind you is likely to interfere with your enjoyment, hiding detail and crowding the sound field in a claustrophobic manner. You will notice I use a combination of dedicated professional acoustic treatments, bookshelves, furniture and a massive stacked log fireplace...all designed to broadly absorb and improve the reverberation decay times. Long reverberation times are reduced dramatically whilst secondary reflections from side walls and ceiling still give a lively feel to the music. Dead sound is NOT the goal (in fact the early reflections help bring out more detail in music.....long reverberations are, however, a nusiance)