I've used this tire for both street and track driving. It has served mostly to get me to and from the track for HPDE's, and as my rain tires on track. I've left them on a few times when the track was dry to test them out as well. I would say they are one of the best street tires that can be used on track. There might be a handful of other tires (RE-11, AD08, PSS to name a few) that are just as good, or slightly better in dry conditions when being pushed to the limit on a racetrack.
Pros: The Z1 Star Spec offers excellent feedback, sharp steering response, good breakaway characteristics, and is very consistent lap after lap on track.
Cons: Noise is not bad for the first few thousand miles, but becomes unacceptable for a street tire after being used for a while. Comfort is OK at best.