Ive used these tires on my M3 for the past year. Lots of spirited driving, 2 autocross schools, one where it was dual driven (about 100 runs just that day.) 6 autoX events where I won class 3 times.
I did have one event that was very odd. Everyone running these tires that day (about 6 of us) all had the same issue with no grip what so ever. It was sunny and about 70 degrees yet it was like driving on ice. Myself, both drivers in a 240Z, a couple people in EVOs and I think someone in an STi all had the same issue that day finishing well down in our respective classes.
In the rain when the tires were new I couldn't break the back end of the car loose no matter what I did. It wasn't till I was autocrossing in the rain after the tires had 14K miles on them that I managed to spin the car for the first time.
Overall I'm very impressed by these tires and will buy another set.