I just replaced a set of michelin pilot sport a/s's on my mercedes and noticed the difference immediately. The michelins are a nice tire with solid dry pavement traction. However, I found them loud on the road. Also, the steering, although responsive, was a bit sluggish for me.
The bridgestone potenza pole position's have a great feel on the road and they are really quiet when compared to the michelins. Plus, they are about $30 less per tire.
I live in the northeast, so I hope to try them out on wet pavement and perhaps a little snow . . . but my expectations for snow and ice driving are realistic. My car is heavy but the torque that the engine puts out will cause my rear tires to slip in snow and ice as it would with probably any all season or summer tire.