They are very good on track IME. They seem unable to fade, especially for what they cost. They're good on the road as well. However they are a little iffy if driving from cold, but I am referring to the car being driven out of a garage after it has been stood up for a couple of weeks. A hundred yards later and they seem to be fine.

Alternatives to them are the Federal 595RSRs and the Yokohama AD08Rs - the former are very good but do not seem to last and there are issues with them cracking although it is not meant to be fatal.