I got my TV delivered on Friday and set it up using the included base. The TV does not sit straight on the base, and I'm going to try loosening the mount screws to level it. The base is ... OK. I don't feel like the TV is going to fall off, but the base is not what you would call overengineered.
Before ordering the TV, my #1 concern with this set (which will be used by my family for gaming about 99% of the time) was input lag. I'm happy to report that when the TV is set to game mode in settings, there is minimal to no input lag from either a 360 or a PS3 connected over HDMI.
The remote was dead out of the box. Since I also ordered the 60" 601ia3 and the 70" 701ia3, and the 60" had already come in, I used the remote from the 60" TV to set up my M650VSE. I'm going to call Vizio today and see if they will send me a new remote. I had no issues while using the remote that worked; the response time seemed fine, and the rear keyboard is a really nice feature. The 60" has already gone to my parents' house, so I am without an official remote for now.
My first impressions of my TV are entirely different from my poor impression of this model that I saw at the store running in store mode. I find the softness / weak color issues that I saw in the store TV are not present on my TV when it's in the normal home mode. Also, my TV is in a room with a lot of uncovered windows, and the semi-matte screen on the M650VSE does a fine job of rejecting reflections. It's not nearly as matte as the Sharp TVs, but I find the Vizio picture to be much better overall to my eyes than the picture on the Sharp TVs.
However: I have two large (6" or so) bright circular clouds near, but not at, the top left and right corners of the screen. They are visible while watching normal programming or playing games. I'm going to try the microfiber cloth / paint roller trick and hope for the best. Also, last night, I had a stuck-on-green pixel in the lower right hand corner. I gently rubbed that, and it became unstuck. These issues, plus the dead remote issue, led me to cancel my order for the 70" 701ia3; I am uncomfortable with the quality problems.
I have the Disney WOW calibration disc and I'm going to see what I can do to calibrate the TV myself this week. Out of the box in standard picture mode, the colors were pretty far off; everything had a green / blue cast to it when watching the 2001: A Space Odyssey blu-ray, and the whites were dingy. Weirdly enough, the default "game" picture setting fixed a lot of the blue / green / white issues with no other adjustments, but the reds are still pretty odd. The blacks are perfectly acceptable to me with little crush in the out-of-the-box settings in game picture mode; the blacks overall are really not bad at all. I do not see banding, and there is NO flashlighting. I have a 32" Sony XBR from a few years ago that I paid $1,400 for and it has horrible flashlighting, so this TV is infinitely better in that regard.
The built-in speakers are, to my ears, pretty awful even considering the low standards for built-in speakers. I went to Best Buy yesterday to look at sound bars, but I found them all overpriced for what you get. I have ordered a nice Denon receiver and the popular Energy Take Classic 5.1 speaker system... so my $1100 TV is now costing me another $700, lol. Oh well, I "saved" $1,700 by cancelling the 70" order, so I guess it's OK.
If I can get the clouds to dim and if the stuck pixel does not come back, I'm going to keep the TV because it meets my no lag / semi-matte screen requirements. I'm hoping it works out because I'm not sure what other reasonably priced set I would buy in the 65" range that has a semi-matte screen.