My first autocross of the season was today. LOTS of fun. I haven't done it for years and I was glad to get back into it. Mine was more of the standard deal - flat parking lot with cones. People run completely stock cars, you really just need a helmet and loaners are available.
I was quite pleased to beat some much more powerful cars and even out ran a Lotus Elise, but I wasn't in my Porsche. I was in my POS '87 Honda CRX race car with maybe 100 Hp. Still she really came alive today with race slicks on. God I wish I could keep those on the car, which is also my daily driver!
That's the fun things about autocross - you can race anything and you can beat just about anything. With tight routes and slower speeds it helps to even things out between the big guys and the little guys.