I tracked mine (Laguna Seca) last August, six days after I got it (umm, it was mostly broken in by then :willy ).
I was also driving a Ford press car (a red GT) at that event. This was for my Ford GT vs GT4 (Gran Turismo 4) story, and I thought the GTs (both mine and the press car) were pretty sweet. That was last August, and in November I drove the Tungsten press car at Willow Springs for our American Exotics comparison, and again felt like it was the most capable of the three (though the Z06, in "Competition Driving" mode, is very nice too). The Viper was surprisingly uninspiring. I think they neutered it too much in the most recent version to get away from it's "crash happy" reputation, but I liked the previous version better because at least you could rotate it when you wanted to (also when you didn't want to, but it never "bit" me...).
I agree that the GT's suspension is softer than a "real" track car's, but between the suspension tuning and the overall "friendliness" of the GT it's very easy to push to -- and beyond -- its limits without crashing. I've driven plenty of "track cars" that were a bit of a razor's edge, meaning by the time you realize you're in trouble -- TOO LATE!
So I guess it comes down to what you're after. I like the GT's more relaxed nature because it translates all the way to driving it at 11/10ths and not biting you in the ass. I know the 360 Stradale, for example, is very capable at a track, but just like the regular 360, if you get in over you're head you're probably going to crash. The "on/off" effect in the Stradale isn't as extreme as with the regular 360, but it's still more than the GT.
JMHO