I have used them on track.
They are one of the best if not the best I have used at handling repeated stops from high speed without fading.
However, the dust imbedded itself in the wheels and was extremely difficult to remove.
This was about 3 years ago so the current Blues may be different.
Yes, I used them at Road America last Octorber, and they have great stopping power. However, the debris they leave on the car is like a toxic waste dump, especially if water gets on the debris.
Per SubDriver, this past weekend at RA I used CarboTech 8's (..I actually ordered 9's for the front but got 8's), and they worked great, but I don't think they 'bit' as well as Hawk Blues on the high-speed track; maybe 9's on the front is the way to go at RA. The CarboTech's did create dust, but it cleans/blows off ridiculously easily.
Nonetheless, I will use 9's on the front May 28/29 at RA.
Forget the Hawk Blues....as mentioned, they eat the finish off your car and wheels. Carbotech all the way. If you don't think the xP8's stop quick enough, go to XP9's/P10 combo. Subdriver did a good writeup on another link. FYI.