I used GMD down here in pompano beach,fl, and like mach_man said, it was absolutely night and day.
My initial reason for going with GMD was that I had blown both my fork seals, so rather than pay the money to just have my forks rebuilt, I opted to have GMD re-do it with the stock internals, then went for the chassis optimization. It was quite pricey, but to get back out on the track with a stock front end, stock rear shock and have it make that much of a difference was simply amazing. The bike was transformed into a different animal that I basically had to learn to ride all over again.
Shortly thereafter, I was able to find an ohlin's triple clicker, and after that I made the decision that GMD definitely had my business from now on. Their customer service down here is outstanding. When i found the Ohlin's triple for the rear, I took it in along with the 10, and they had it checked out, installed, and set for me within an hour, all at no charge. Another time, I went down at the track, brought the 10 up to them because I was scared of my forks being tweaked, and they checked it out within 20 minutes, made some adjustments, let me know it was good to go and I was on my way, free of charge. (i've seen/heard of many stories where people take their bikes in for the same thing @ other shops, only to be told that there is some damage and then charged a nice amount for it.)
all in all, I'm a firm believer of GMD's system and methods, and for me it was worth the money.