lets keep this realistic - the only perfect black screen you will get is something that is not backlit, but is something like AMOLED or SAMOLED.
What we can hope for is an evenly backlit screen- you will always get some sort of milky effect, check any LED backlit LCD screen in a TV or otherwise, even a computer screen.
QFT. Note this 2-year old Dell 19" monitor. I never much liked it, but my kids haven't complained:

I am definitely not saying that some crap monitor from Dell is or should be the standard. My standards for an iPad are way higher. And I have exchanged my iPad 2 for one with tolerable leakage (scroll back a few pages for mine.) But "tolerable" and "perfect" are not the same thing IMHO.