Yes! I love it. I've designed many a dream guitar (and some nightmare guitars, too).
I think it's a really fun tool. I've been probably 20 times and I find myself designing the guitars I already have, basically.
I find it funny that the tool lets me explore lots of possibilities, but I keep ending up with either a tele or les paul body, a not-too-wild top in green or blue and P90 pickups.
USA Guitars has the tool on their website so that people can design the guitar they want and ask them to build it.
I think it's a great idea. The next step is to have sound clips so that you can hear what the different pickup and body combinations sound like. That would be killer....