Newbie to posting here and not sure how to reply to specific parts of specific posts, so I'll just post in general. I've noticed some posts indicating people having issues accessing 3D content through DirecTV channels on the M3D651SV. Here's what I've had to do in order to view 3D content from DTV
I'm using DTV's HR21-200 receiver and run HDMI directly from the DTV box to one of the TV's inputs. While I believe DTV says its receivers should automatically recognize 3D TVs and no adjustment is necessary to view 3D content, I found this was not the case for me. DirecTV DID recognize my TV in one sense: 3D channels 103-107 that were "grayed out" in the on-screen Guide with my previous (non-3D) TV, suddenly showed up as available when I hooked up the DTV receiver to my new Vizio. But when I tried to play Channel 107, instead of all the conversions taking place automatically, I got a "split screen" effect - essentially the same picture side by side.
Using the Vizio remote, here's what I had to do: MENU > 3D > 3D again in the "Output Mode" box > select SENSIO in the "Content Format" box. Then select "OK" and watch with your 3D glasses.
When going back to 2D content, you have to go through the same basic steps: MENU > 3D > then change to 2D in the "Output Mode" box.
In other words, you have to change the settings on the Vizio itself to watch 3D content from DirecTV.
I've only watched a few minutes of 3D content so far, but the effects seem pretty good to me. No complaints. I also have a new Sony BDP-S590 3D Blu-ray player hooked up directly to the TV via HDMI. I haven't watched or even tested any 3D discs yet, so not sure if I'll have to make the same menu adjustments for that, but I suspect I might.
So far I generally like the TV. I'm not a true videophile and don't spend endless time tinkering with the settings, but I do like things to look relatively "real" or authentic. I also like a fairly bright picture - or perhaps it's just that I don't like watching a picture where the colors seem "dull" - so I tend to crank up the brightness a little. Other than that, the only real changes I've made so far is to turn off the "Smooth Motion Effect" in an effort to get rid of the "Soap Opera Effect" many others have commented about and which I noticed. The colors on the TV seem pretty good to me; my only complaint (minor one) is that it seems in some shots, particularly indoor studio-type shots, that there is a little more yellow than I like. I haven't tried to fix that yet and not even sure it's a problem, but wondering if anybody else has noticed the same thing? But sporting events and anything shot outdoors looks very good to me. All in all, pretty happy so far.