While I know individual new iPad units have differences in screen quality, tint/hue, and brightness (I've seen the proof in several forum posts here and elsewhere), I don't buy the premise that there are "perfect" screens.
When people use the word "perfect", what they're saying is, "I got an iPad and its screen looks acceptable to me." That so-called perfect screen could be handed over to a more discerning/particular person who could find something wrong with it.
Given the variance and array of minor differences unit to unit, I tend to agree with spcdust that you're not going to find the elusive "perfect" screen, because it doesn't exist. The test is simply whether or not the owner is satisfied.
I do think it's a fact that the new iPad in general has a different color temperature than iPad 1 and 2.