UPDATE 2: Daring Fireball checked with source at Apple's iPhone Engineering who confirmed that:
there were no changes regarding display color temperature between 5A345 and 5A347, and that there’s no practical reason why someone with an iPhone with 5A345 installed should go through a complete system restoration just to get 5A347.
And that, while there did appear to be differences in "yellowness" from iPhone 3G to iPhone 3G, it was not due to firmware (perhaps components?).
