I have used the cr6zz tyres in 15" on my GTD for quite a few years now and they have the correct look with deep sidewalls and have good grip in wet and dry. The deep sidewalls also help with giving a decent ride on the apalling roads in this country. The tread pattern is not heavily cut so they don't like standing water or puddles but otherwise very good as the rubber compound is pretty soft. They have a theoretical max coefficient of friction of 1.33.
The wear is not too bad and I have used them mostly on the road with some time on track.
They are however a bit expensive so I had a moan at the guys on the BMTR stand at last year's Autosport show about the price. I said I was very happy with the tyres but the price could do with coming down a bit as the moulds must have paid for themselves by now. No luck yet so due for a repeat moan in January.