Ignore the hate.
The issue with the M3 board is mainly that the Rev1 board is under powered(actual amps, rather than performance), and it tends to run hot, so it should have some heat sinks added.
Like all low cost SBC's there are a lot of compromises in its design such as having only 2USB's and the SATA not being true SATA, so its SATA is slower than a true SATA board (but true SATA costs...) At least you can connect a SATA device to it..most other boards won't let you do that out of the box.
But, as with most things your choice of SBC will depend on what you want it to do. The M3 has processing power aplenty, when it has enough amps, make sure you use a 2amp on the Rev1 and get a 3-4 amp power unit for the Rev2.
The Rev2 model should cope with a USB hub, but for any low ampage setup, its always best to try to use a powered hub if you are going to connect a lot of other devices to the USB. So they don't drain the boards power allocation. I only have a Rev1 so can't be sure the power issues are fully resolved on Rev2, but on paper they seem to be with the new power input.
As for image processing, that depends, what do you mean by that? If you are talking CPU based manipulation of image data, then the M3 is fine for that, so is the Orange Pi, (it also gets overhot) or any of the other quadcore systems on the market, they all have their plus and minus points.
If you are planning to render and display in real time though, the M3, and Odroid Xu4 have the best graphic chips of the sub $100 systems. But you'll probably need to write your own software to do it, as most software for these machines has not learned to use the specific PowerVR and Mali 600 GPU's.
hope that helps...