We just got the 80" Vizio M80-D3 and ... I'm pretty underwhelmed. It replaced a similarly sized Mitsubishi DLP we'd had for almost a decade and, no doubt, the picture is superior in every single way. That's not my complaint.
But there are quite a few things on this TV I really, REALLY do not like. Starting with a small, but nagging issue ...
The flimsy, widespread metal legs. Maybe they mean all these TVs to be mounted, but in our Great Room we have a large, shallow shelving area designed for a TV to sit on a shelf, so that's how I want it, but the legs are both so wide -- more than 4" on each side -- and yet totally unstable, the TV feels wobbly if you brush against it AND can't be placed closer to the front edge of the shelf, leaving a weird-looking set-back. (The legs also bounce a bit, like bent paper clips, if you push down on the set.) It may be a small thing, but when you buy a TV this pricey it should look good, aesthetically, and not like dorm room Ikea furniture.
EDIT: I lied. I just measured, and the bent-paperclip leg extends almost 8" from the TV front on either side. So the TV MUST be set back at least 8" into any cabinet/shelf. My old unit the front of the TV was just about flush with the cabinet face, and our only other non-hung TV (55"), which has a single stand, also only has 3" from the TV front to the front of the stand, plus feels more stable the the Vizio. (see: http://i68.tinypic.com/29legbc.jpg
Second small(ish) gripe ... Why, WHY doesn't this thing have a tuner? They are a super cheap addition that pretty much every other set has. It would be one thing if it was a small add-on, sold by Vizio (maybe something that plugs into a USB port, or a little HDMI stick). That I would be fine with. Heck, I'd pay $50-$100 for it even, so a nice little profit margin, but I hate not having it, especially when there are no easy solutions, even more than I thought I would. Over-the-air TV is essential where I live for storm situations. I've got my TV plugged into a battery backup, so when the power goes out, the TV can stay on for at least 30 minutes and with antenna, I can keep watch on the weather, easy peasy. I was hopeful a computer-style USB-stick solution would work, since past Vizio USB ports recognized media sticks, but it doesn't. At all. In fact I can't find a dang thing the USB ports are useful for.
I also wouldn't mind the above much if TV tuners were a readily available third-party commodity. They're not. The only real options out there that I'm finding are cheap, clunky, pieces of junk geared towards grandparents with TVs from before the digital switchover. No thanks.
My biggest gripe though is that the entire tablet/"cast" system is a POS. Definitely not ready for prime time. I don't want to start a Google account just to be able to use my TV remote, thank you very much. Casting Hulu, or whatnot, is glitchy, at best, failing more often than not. Just. Useless.
And, yes, I can work around all of these things. I have a Harmony remote that will control the TV. I use DirecTV boxes and Apple TV anyway, so don't need those things to work, but they should, for the cost.
We recently got a close-out Samsung UN 55" 2015 model for our bedroom. The picture is amazing. The Smart TV features are great, and I find myself using them over the attached Apple TV in there, and the built-in tuner is amazing. Heck, I've realized we could probably cord cut completely in there, if we wanted to, and just use the TV and its built-in apps. And that's all for something I never thought I'd touch when buying the unit.
Altogether I'm kind of unhappy, and hoping I'll grow to love it. So far, though, I'm definitely disappointed.
BTW, if anyone's got settings advice for this, I'd love to hear it. The picture options seems a lot less granular then the Samsung, and I'll note that after adopting, and then slightly tweaking, the calibration settings some kind soul posted here, the picture there is really, REALLY good. Better than the newer version Vizio, for sure.