While not "slicks" exactly, I have autocrossed both my Focus and Mustang on DOT race tires. They had some evidence of tread existing, but were shaved. I ran Hoosier R6 tires on the Mustang and a few different sets of BfGoodrich Comp T/A R1 tires on the Focus. The Hoosiers had a long heat up time for autocrossing since they were road racing tires. The A6 was what I needed to run instead. The hardest part of running race tires is the hassle of storing, hauling, installing, and caring for them. Storage and care is vital to keeping the tires working properly. They can't get too cold or too hot in storage. I used to have a nice climate controlled area to store all of my different tires, but when I lost that ability, storing tires has become difficult. As for running them in an autocross or on the track, they were fantastic in every way! It was amazing how much different the car performed on the tires. Braking is where I saw the biggest difference. I could brake far later than I would have ever thought possible when using race tires vs street tires.