since the yellow screen was a big deal when the 3G came out, the first thing i did when i got my 3G S was to compare the white balance against the 1st gen iphone (i don't have a 3G). and yes it is very yellow or "warm" versus the original iphone, but it also makes the original iphone look too "cool" and the whites on that have a very blueish/purplish tint.
not sure if it's worth bringing it to an apple store to have replaced. i have no way of knowing how other 3G S phone look, for all we know they all have the same yellowish white balance. i'm curious to hear the results from others who do go to the apple store. for those who did go, what did the geniuses say? where you able to compare to other 3G S phones? did you get a replacement? if you did get a replacement, are you now happy with the white balance?
this could all be fixed if apple put kelvin adjustments into the settings so we can manually adjust the white balance our selves.