I was in the Apple Store yesterday to get my black one replaced under warranty, I updated to 4.2.7 on accident and it messed up my jailbreak and made it so Safari wouldn't load. After restoring it from an old backup, then restoring as a new phone, my safari still wouldn't load right, and I couldn't use any of my jailbroken stuff. Contacted Applecare and went through all the steps of repair with them and they finally just told me it needed to be replaced.
I asked about replacing with a white one, but Apple's policy is they have to replace the defective unit with the exact same part number, and the white iPhone is a different part number so that wasn't possible.
I was on a waiting list for the next available sales person (the store is ALWAYS super busy) and then talked myself out of buying the white one at no contract price ($599+tx) and selling my black 32gb.
I honestly didn't notice any difference between the official release white iphone and the white one I had from a conversion kit when I was on T-mobile. I couldn't find a white conversion kit compatible with the Verizon one, though.
My main concern with the white iPhone 4 is do they all ship with 4.7.2 (or 4.3.2 for GSM)? If so I would have to wait for a jailbreak which would cripple my phone usage. Anyone with the official white care to let me know what software they are running?
The replacement 32gb black I got yesterday had 4.2.6 on it so I was very happy.
Sorry for the long post, but I figured some of this info might be useful to you guys.
