The enduro is brutal. They've just made some changes to the track though to make it a bit safer. The hill on the inside of 3 has been knocked down from what I've heard. Cars tend to get flipped and roll there.
Its probably my favorite track though. The elevation changes are awesome, they're are some fast turns (esp turn 1), and its long.
You can get 'em new from Panoz for like $50K. Or, you can buy one used for a whole hell of a lot less, like $30K or so I think. I was driving a friends, cause I have 6 friends who all have them. Its a cool option for a racecar. The body panels are molded ABS, the front clip comes right off, etc. etc.
To give you an idea how they run, the fast Panoz guys are in the 1:59 range at T-Hill. If you were to put a stroker in one it would be wicked fast, they're just down a little HP on the straights.
In March I took second in Prepared Class at viper days with a 2:11. JoeB won with a 2:09, these are on street tires. I was running 2:16-17 until I put new rotors and brake pads on. Thunderhill is very hard on the brakes, but its my favorite track you'll love it.