I did a full factory reset last night, as well as a power cycle. Smart Dimming still definitely doesn't function as it originally did pre-1.60 where you'd see the lights move on the edges of the screen, but they weren't ridiculously slow to react as they appear to be now. It's not as bad as the original 1.60 firmware where it was painfully obvious, but it does indeed still blow out brights when transitioning from a dark scene.
That said, I did re-calibrate my TV as well using the WOW disc last night. PQ is still rock solid. Here are the settings I settled on for the 2013 50" M.
Backlight - 60
Brightness - 59
Contrast - 74
Color - 45
Tint - -1
Sharpness - 0
Gamma - 2.2
Black Detail, Smart Dimming, Smooth Motion, Reduce Signal Noise, Reduce Block Noise, and Game Low Latency are all off.
Overall, super happy that I no longer need to go in and turn SD off every single time I turn my TV on, but rather disappointed that a feature of the TV still doesn't function as it once did. I'm also pessimistic when it comes to Smart Dimming ever actually working correctly. If they didn't fix it with this one, I doubt they ever will.