A few years ago I bought an Aprilia Mille, which was fitted with Michelin Pilot Sports (can't remember which one exactly, but there were a lot of R's on the end).
Turned out they were pretty much the stickiest track day tyres you could fit at that time.
It was Easter when I bought the bike, weather was cold and damp, and it felt like I was riding on ice. This was because it was not feasable to ride quickly enough, on the road, in that weather, to get enough heat in the tyres to make them work properly. If I could string about 6 corners together at decent pace, then I could start to feel the tyres getting grippier - but if I had to slow down, the tyres cooled down and I was back to square one.
The point is this; The ultimate grip from these tyres was phenominal - but on real roads in cold or damp weather they were just plain scary.
After scaring myself sh*tless for a couple of weeks I binned the Michelins and put on some more road friendly tyres and completely tranformed the bike and my confidence.
There's a lesson in there somewhere
Phil