I 've also put michelin cup tires to my 997s and they are not bad. The ABS comes very quickly when braking because the michelin need a lot o warm up, the noise level has also increased and the ride has become firmer, but the grip difference is so great that I don't care about these things.

A friend of mine has told me that the Hoosier semi slicks are a lot better by the way. I will try them next year!