I'm new to this message board, but if I may add my 2 cents... I bought a TRX after a trainer friend of mine was introduced to it by Todd Durkin (www.todddurkin.com) on of the top performance trainers out there. He trains all of his pro athletes (Drew Brees, Reggie Bush, LT, Shawn White etc...)on the TRX. After doing some more research I found out that another trainer, Peter Twist, trains Justin Morneau on the TRX too.
I was still a little skeptical but after buying one (I got the one they sell to the military) and using it for the past few months I can honestly say it worth every penny and more and I now know why these guys are training on it.
First the quality of the product: This thing is built like a tank, and it has many more features than meets the eye. The straps need to be micro adjustable depending on the exercise, the footcradles allow you to do the best core exercises I've ever done, it comes with 2 anchoring systems, a DVD, a 12 week training program.
Second, the exercises are really functional and unlike anything I've done before. I've been big into bodyweight and functional training but the core and rotational exercises are awesome. I also use it to do my stretching and and warm-ups (you can hook it up to a chain link fence).
Bottom line is I've spent way more on a set of dumbells and a pull up bar than I did for this and this thing is way more versatile and functional.
I don't think I could build something of this quality and with all the little features and I still wouldn't have the programing/instructions etc...