I just picked up a set of these from TireRack.com about two weeks ago. I replaced the stock Bridgestone RE040's and all I can say is WOW!
My IS feels like it's stuck to the pavement and it's more willing to get around turns faster. The best part though is that they soak up bumps much better than the bridgestones and transmit a lot less road noise. So the ride is smoother and my IS handles better... how could I not be happy?
I haven't really pushed them in the rain, so I can't say what the wet traction is like... but overall I'm really pleased... compared the to the stock 040's anyways.