I haven't been able to find NT555RII in the size I wanted to try out and bought M/T ET Street S/S instead.

From what I've read and heard talking to people who run the NT555RII at the track, the ET Street S/S works better. The Nitto drives better on the street and should last longer, but you're still talking a soft compound tire with a limited lifespan. A couple of people mentioned the NT555RII losing its grip after being heat-cycled from burnouts even though there is still a good amount of tread left.

Wish I had more firsthand knowledge, though.