Phil,
Viper swears by the Toyo 888s he has on his S1 - he says the grip is immense. I am sure he will throw his opinion into the pot when he next logs on but I understand that they are quite soft and therefore wear quicker than other tyres.
At Goodwood and Gurston, I had Goodyear Eagle F1 Asymmetric fitted and found them to be excellent - very progressive and grippy; however, I did find (at Goodwood) that they became unsettled if the pressure wasn't correct. This isn't a real criticism as much as something to be aware of.
I have Pilot Cups before but never tracked them - so can't comment on how they perform; however, for road use they were excellent albeit not as progressive as the Eagle F1s.
