I went to an Apple store in Century City, CA to exchange my 64GB wifi purchased on launch day. The unit I received back is serial number: DLXFKG and shipped with 4.3.1. While my initial unit had severe light leakage, this replacement unit only has a tiny amount along the right and no dead pixels.
The Genius informed me that the current policy is to allow a single exchange for a new unit, but that there is no guarantee that the unit will be better. However, he did say that they are specifically testing these new replacement units for the light leakage issue. He said that after a single replacement Apple could offer me a refund, but not another new unit.
At this point, given the improvement with the newer iPad, I think I am going to hold onto this one until the newer LG and Samsung screens make their way into the supply chain. Given the long ship times, it would not make sense to receive a refund. I have not seen many reports of even the most recently-manufactured iPad's being free of this issue.