Sadly my screen is a little discolored too. Mine will get swapped in a few days though, since I have purchased Applecare+ and can therefor use the express replacement service of apple for free. Since this device is so expensive I'm not going to settle with "okay", as I was kind of underwhelmed by the screen quality too.
This is however just a part of the technology. Due to the manufacturing process it's really hard for Apple to get the screens perfect. Since most people usually don't notice it even if it's obviously there for people like us, Apple is better off just replacing the iPads for the people who are bothered by it than by than by discarding probably over a half or 3 quarters of the screens made.
There are good screens out there tough, as they're obviously designed to be uniformly white (the manufacturing process just makes it hard to actually realize it). There are iPad's with only imperceptible color gradients.
I've gone trough several exchanges for any iDevice I've had and after a couple of tries I always have gotten a screen I can happily settle with.
Though one thing I would highly suggest is: Try not to be bothered by overal tints (unless it's really, really bad, but that doesn't happen too often as far as I know). The overal screen tint, unlike color gradients, is usually not noticeable unless comparing screens. While I do believe there are probably screens with no (noticeable) color gradient and with a preferable tint, and while I also would like to have on of those myself, setting both those things as a requirement will probably make it near impossible to get a screen that you will be happy with.
TL;DR:
If the screen is not uniform get it replaced, Apple probably won't make a fuss out of it (from my own experience), if it is uniform but doesn't have the most preferred tint, I'd highly suggest keeping it.