TRX Trainers: Worth the Money?

The buzz around the city these days (in addition to the millions of pilates and barre studios popping up EVERYWHERE- and even though they are everywhere classes are ALWAYS full) is a new tool called TRX: and classes involving these are filling up faster than a class at Soul Cycle. So what is it exactly? Basically, it's a rope-like system that provides a suspension based workout. It seems pretty interesting, and something that might be a great workout alternative when I don't get out of work early enough to make it to one of my usual group-ex classes. I can even hang it from my door in my apartment! Talk about super convenient, not to mention vacation or travel friendly!