i have fitted square set-up on my e36 m3 3.2 track car, specifically built for nurburgring. i ran (on recommendation to me from race drivers of same car), 4x 235/40/17, square setup - and was advised best to use the 180 street compound, rather than the 120 track. this apprently is the better tyre as grip is equal to the 120, but they handle the heat better.
the tyres, for the money, were fantastic. this was the first time i have used the car on track, since its been stripped etc, so i dont have much to compare to... but generally.... the grip was very good, maybe not quite as good as a r888, but certainly in line with federal 595-rs if not slightly better, but im comparing that to on another car so its not a fair comparison.
the tyres look great, and are quite wide tread pattern. they have a small rim protector too. they gripped well both in dry and wet. the broke away safely and progressivly, and didnt get overheated etc. i did around 40 fast laps of the ring (8.12 BTG is my best time on these tyres). i ran them quite hard pressures, again on recommedation. 32 cold, aiming for 40 hot. this seems high, but works.
best of all was the tyre wear. i did 1000 miles to the track and back on motorway, and 40x laps at a good pace... and they are hardly worn at all. infact they still look virtually new. i would expect less than 1mm had been worn away, and they come with 7mm from new i think anyway.
overall a very good tyre for the money, and certainly worth trying. they are half the cost of r888 and i think they are likely 90-95% as grippy... but thats just my expectation. would be interesting to compare them to other tyres in the future, but for the budget minded trackday, they are great