The screens ARE different...please read on!
I got my iPad 2 today and there IS a difference between the iPad 1 and 2's "whiteness levels", so to speak. I've seen this before. The iPad 1, my particular model anyway, has an incredibly sharp and super bright white screen.
Conversely, I want to say that the iPad 2's white screen has slight "yellowish" undertones, doesn't it? I'm doing apples-to-apples comparisons, e.g. the Settings --> WiFi page, which is consists of lots of white background. The iPad 2 does not appear as super crisp as the iPad 1. They're definitely not identical. Are they calibrated differently maybe? I'm not even saying it's bad. There may be a lot of people who prefer the iPad 2's "warmer" white to the iPad 1's.
I've seen this before with BlackBerry's and it's driving me crazy. The iPad 2 has a "warmer" white "tone" to it, maybe that's a better way to describe it.
What do you guys think?