^ my MY06 also vibrates during A/C idle and u can feel it through the steering wheel. but pretty much all cars do that anyway.

I dont get an idle rattle though. Sound ricochets through the car so:

1) Make sure the A Pillar seals on the outside are pushed in properly.
2) Lower the front windows down a centimeter and see if that solves the rattle.
3) Make sure there arent any loose objects such as sunglasses and coins in the various compartments in the cabin.
4) Lightly thump parts of the engine bay to determine whats loose.