Well I just bought a 06 GX with a build date of 7/06 so I will update here if my GX develops the clunk. It had 14 miles on it. Took delivery on 9/18/06, so I basically got it as soon as it was delivered to the dealers lot!
Some phones will not be able to transfer any of the contact from the phone to the the GX by bluetooth. Check lexus.com for phone compatibility issues and check to see if your current model phone is capable of doing this. One contact transer is better then none. I did one at a time and only put the essential numbers in there. Everything works fine if you have a compatible phone for the GX bluetooth.