Tweak Rating: 9/10
This tweak provided a significant incremental sound improvement compared to other tweaks. The only drawback would be spouse resistance since the panels are rather conspicuous in a room. However my spouse commented that I did a good job cosmetically in building the panels.

Other Tweaks:
- Vibrapods
- Raising speaker cables off the carpet (using foam water pipe insulation), JR tip.
- 3 dedicated AC lines for my HT system (15A, 15A, 20A) with hospital grade plugs
- DIY power cables, VH design. Soon to try DIY with JPS in-wall AC cable.
- Monster HTS3500 power line conditioner all equipment, except for power amp and CD player which have dedicated AC lines.
- Upgraded speaker cable from Monster XP HP to Kimber 4TC and 8TC.
- Upgraded interconnect cables from Monster Interlink 400 to Homegrown Audio Silver Lace.

Details:
I built two panels using JR's recipe.
- 6.5 feet high
- panel area 28"X68"
- frame made with 1X4s
- Roxul "Safe'n Sound" sound insulation (I used this instead of fiberglass since I had it lying around)
- panels 4 inches from the room walls, 1 foot and 3 feet in front of main speaker grilles. Note: I have a door on one of the walls, therefore necessity of 3 foot distance.
- labor 6 hours per panel

My System:

References:
Jon Risch - DIY ACOUSTIC TREATMENTS - Acoustic Absorption Panel.
http://www.geocities.com/jonrisch/a1.htm
and
http://www.geocities.com/jonrisch/wp.htm

A similar article/design can be found at this link.
http://www.audiorevolution.com/equip/index.html
select 'How To Articles->Home Made Room Treatments'