Samsung's MAP for the PN51E7000 was lowered to $1499 recently. The E series will have a dual core processor in it, making apps run faster and smoother, be able to multi-task and also adds a web browser. According to Samsung, it will also have a 10% improvement in black levels over the 2011 line. It's up to you if these improvements are worth an extra $200.
If I can find a better deal than I'm currently seeing on the PN51D7000, I am going to pick one of those up. Otherwise I'll wait for the new Samsung and Panasonics to come out and hear some reviews on both of them. I'm curious how the improved brightness in Panasonics compare with the 2012 line of Samsung.