For what, exactly? Sound treatment?? Sure, it will help tame *some* reflections, but you have to know what the problems in the room are before you try and "fix" them!
For sound-proofing, it won't be worth anything -- for that, you need mass and isolation - generally meaning some serious construction.
I want to improve my mixing. All of my music comes out booming. I am not so interested in keeping the sound from leaving the room/garage. I just want to stop the reflections so I can hear exactly what is coming out of Ysm1p monitors.