My dad, wife and I went on Friday but because of work we couldn't get there until 3:30. So we went straight to the passenger cars to qualify for the SSR/Z06 track. Then to the SUV's to qualify for the H2. Then the luxury cars for the duration. My impressions of the cars I drove follow:
Passenger cars
Pontiac GTO - Overall I like the car. Great sound and awesome power. My only problem with the car was the steering. I felt like it was overboosted. Seemed like I would turn the wheel and have to wait for the nose of the car to come around. I would say it would be a great everyday car but maybe not a great autox car.
Pontiac Grand Prix GTP - Nice driver also. Steering felt better than on the GTO. But the car is just too darn big for my taste. And the manumatic is a waste in my opinion.
SUVs
Cadillac SRX - First let me say that I HATE SUVs. Maybe it comes from driving Miatas for 6 years. They are just too damn big. But I like the SRX. It is more like a big station wagon than an SUV. Smooth, quiet, comfortable. Everything you would expect from a Caddy.
Hummer H2 - This thing feels HUGE!!!!! It is solidly built (expected) and comfortable (UNexpected) The big hill you drive over was an interesting experience. Not being able to see anything in front of you and all. Fun drive just wished it was longer.
Luxury Cars
Cadillac CTS Manual - I agree, the manual tranny on this car is wasted. If this were a CTS-V it would be a different story. I could see renting this car while on vacation. It is very comfortable and does have a good bit of pep.
Lexus ES300 - I have always loved Lexus. This one though, is just an expensive Camry. Not much fun on an autocross course.
Saab 9-5 Aero - Man, you can feel it when the turbo kicks in on this car!!!! Once it is on boost it has great power. Finding the key is a bit if an issue though. Saab feels it necessay to put the key within easy reach of the all passengers in the car. (must be a Swedish thing!)
BMW 325i - I LOVE THIS CAR!!!! Now I see why BMWs are called the Ultimate Driving Machine! I took my Dad with me on this one after driving the course a few times. When he sat down I said for him to hold on. I drove the course like there was a $2 plaque on the line. I think I scared him a little.

It was fun.
Chevrolet SSR - This trucklet has alot of the elements right. Great engine, great sounds, great looks, drop top. The one thing it lacks is structural rigidity. Every time I would throw it into a turn, the thing would creek and moan like like Bob Hope getting out of bed in the morning! It would make a fun car for the Woodward Dream cruise.
Chevrolet Corvette Z06 -
WOW!!!!!!! This car is fun. My "instructor" is an British Forumla Ford driver from somewhere here in the states. He gives me the insurance/lawyer spiel about not spinning and stuff. It went in one ear and out the other.

I had fun driving it and now I have to get one. Not really! When we get done with the run he turns to me and asks if I've done this before (keep in mind that I'm wearing my AutocrossForum.com shirt, he wasn't very observant). When I told him that I autox a Mustang, he said he could tell.
All in all I had a great time and hope they come back again, though I think it is unlikely. Talking to the people who were working the event, they said that they had long lines for all cars at all times when they were in Orlando a few weeks ago. But we can always hope!!