The Vizio M Series LED TV is great, but depending on the size and your usage, you might prefer to get the cheaper E Series instead.
The Vizio M Series has better uniformity than the cheaper E Series and more effective local dimming, too. It also adds the motion interpolation feature. However, depending on the size, it might have a significantly lower contrast ratio (but better viewing angle). If you don't plan on using either the motion interpolation or the local dimming, get the cheaper E Series instead.
The design of the M Series is less bland than on the E Series. It is thinner, and the frame has a brushed metal finish.
The gray uniformity of the M series is an improvement over the E Series. You can no longer see the individual LEDs behind the LCD layer. However, narrow darker bands create a dirty screen effect on panning shots.
Our unit had an excellent viewing angle. The saturation of the colors stays great. This also depends on the size. See the Q&A section for details.
The motion blur is average-good for an LED. Contrary to the E series, the 'Motion Blur Reduction' feature does not reduce the blur (see the Q&A section for details).
The remote is more advanced than the one available on the E Series. There is a full QWERTY keyboard on the back of the remote.