In what way is it "extortion?"
Did Apple force you at gunpoint to purchase an iPad 2? No?
Then you can return it at most retailers and of course at the Apple Store unless you ordered a custom-engraved device.
As far as complaints go, it largely depends on whether the issue is important to you or not.
Pointing out this issue is like hanging around a Porsche dealership demonstrating how some of the dash trim pieces can rattle - a valid point, but only a certain percentage of people buying a Porsche will care. (Even more to the point, if you try to get that rattle fixed, they will generally try two or three times then you'll be told your car is "functioning as designed" and Porsche will not pay for any further attempts to fix the issue under warranty. Alas, there's no option to return your car.)
So what I'm trying to say (I'm still not an Apple employee) is the iPad2 is what it is. If you're annoyed by the display's shortcomings in manufacture, return yours now for a refund if you can, and I suppose you can keep trying to exchange it as long as Apple will continue to do so.
But obviously if it's just the nature of the parts used in the product, that very likely won't help, so a mention of the multiple exchanges might still get you a refund, depending on who your original merchant was; talk to a manager if need be.
I'm not trying to be an apologist, just pointing out how the consumer electronics marketplace actually functions in most cases.
If you want to continue to lobby, I suspect as was the case for the iPhone 4 what you may win from Apple is an extended return period rather than any change in the product's design per se.
