I just purchased the new ZIIs and ran them for a day at a POC time trial at Willow Springs, and I was very impressed. The dry grip is excellent as expected, but their greatest asset to me is the steering response and communication. I can really feel subtle changes in grip through the steering wheel and seat, which is invaluable for track use. I was the only car in the run group on true street tires (all of the rest were R-comp) and my times were top 6 out of the group of 20 or so). The rear end grip in the slower uphill Omega section of the track was particularly impressive.
I had 7-8 sets of the Z1 Star Specs for track/street use in the past few years, as well as a couple sets of Hankook RS-3 since then. The Z1 Star specs are the best all-around tire that I have experienced in terms of a dual-purpose street/track tire and dry/wet grip for the money. The Hankooks have excellent mid-corner grip in the dry and are dirt cheap, but I felt the sidewalls were too soft and the steering response/communication was not as good as the Z1 Star Specs. They also had no grip in colder ambient temps (below 60 F) and in the wet. The Z1s had excellent grip during the wet track days that I ran them on and would only hydroplane in deep standing water. Judging by the massive tread blocks on the new ZIIs, I am not sure if they will be quite as good as their predecessor in the wet. However, I did have to drive through some slush/light snow in 30 degree temps for a short period on the ZIIs on the way to Willow Springs (which is of course NOT recommended with this type of tire!) and they actually did pretty well! The excellent communicability of the tires conveyed that there was not much grip available and I never felt unsafe. I will report back after more track events (I will run them back to back with my Toyo RA1s at Streets of Willow this weekend), but I am extremely satisfied with the ZIIs so far!