In the two weeks that I've had the Z, I've washed it 4 times. Call me anal.
On the last wash, I noticed the brake dust really starting to accumulate inside the wheels. So I wedged my hand in there and cleaned up as much as I could. Hard to get it all near the calipers and the front rotors are close to the wheel, so I couldn't really reach deep in there, but I got as much as I could.
http://www.jaber.net/corvette/images/IMG_4244.jpg
http://www.jaber.net/corvette/images/IMG_4245.jpg
It'll probably not last long as these brakes give off a ton of dust, but boy do those wheels look clean when you wipe 'em down!