I bought mine in Feb 2013, and it's got the problem. Mine's on about 30-40 hours a week, and the spots pepper the bottom half of the screen.
I only see them if the screen uses a lot of white, which does happen every time I start my Xbox 260. It hasn't been that annoying, but I have a few months left with CostCo and I did buy the SquareTrade extended warrantee for it, as well. I suspect that I'll call up CostCo in the December time frame to see what my options are, at that point.
Funny thing is that when I bought it, I had my mind set on the Sharp 70", but when I got to the CostCo, in a side by side comparison, the Vizio TV looked much brighter and crisper, so I changed my mind and got it, instead.