Had the same problem with the stones on my car, but it might have something to do with them only having 3mm on them
Changed to MPS, now they've worn down 1k miles they are brilliant and so much more progressive in the wet. It's certainly not a car you can learn all it's abilities overnight though.
I've got the stuttering, spluttering cd player when cold, waiting for the dealer to reply with a replacement. They took the cd player out and scanned the serial number for some reason - watch this space.
My biggest moan is rear clicking driveshafts, had them "replaced" under warranty but I think the dealer just turned them and greased them - will be back for yet another day in the dealer. What a pain in the backside.
Still wouldn't swap the car for the world, nothing else comes near for the money.