I can attest that I've been through three iPad2's before getting one that didn't have a light leak. And I'm not talking about a small nit or a slight systemic imperfection with uniform light leakage all around - the light leaks were all significant and notable, about the size of a quarter. And were so bad that they weren't even contested by the store staff.
So my fourth iPad2 is perfect. A linemate's iPad that he opened in the store was perfect; the family next to me however did have a small light leak.
Generally speaking, every light leak I saw was ugly and notable. This wasn't that slight "bleed" that you can just accept as part of an LCD. These were all ugly, large yellowish-white blemishes leaking out.