Update: Well I am exchanging my M701d for a 64" Samsung F8500 Series plasma which will be delivered tomorrow. Just a heads up, with the Panny's gone, the stock on these are very low as well and with the talk of not knowing if Sammy will still be doing plasmas, I don't expect these to last much longer if anyone is interested in any of these models.
I will post my impressions on the new set in the appropriate thread from here on out. Good Luck with your M-series and hope it works out for you all. I have a feeling the 2014 models will be much better but I can't wait that long.
I had considered that Samsung too, but in the end the significantly higher price tag for a 6" smaller screen size, and the active 3D, made it a no go for me, even though it will probably have fewer screen issues than the Vizio.