So, after about 180 hours on my third 64D7000 panel the pops have appeared. Turning on CinemaSmooth takes care of the suddenly rising blacks and fortunately I don't see any negative impact on black level (not saying it's not there, just saying that it's not enough for me to tell). However, this panel also has what I assume is what people call hockey pops i.e. sudden changes in light output when watching brighter scenes, and this issue is pretty bad. I wanted to see how much worse it would get with CS off, and much to my surprise disabling CS made the hockey pops stop completely. By now I'm kind of baffled...
My first panel developed flashing red pixels after maybe 800 hours with the logic board fix applied. Therefore, although I have absolutely zero evidence to suggest there's a connection, I'm hesitant to apply the fix on this panel. I'm also a bit suspicious since Samsung never made the fix widely available. Why not, if it works and there's no risk? I only have about one month left on my warranty and don't really want to rock the boat with the set (PQ is great, no pixel problems etc). But it seems both kinds of pops can be dealt with by turning CS on or off:
For brighter movies, especially if they're full-screen i.e. true 16:9 or close (lots of light output), turn CS off to avoid hockey pops.
For darker movies, especially if they're letterboxed, turn CS on to avoid popping blacks.
My set is only used for BD movies so that simplifies things for me a bit.
This is where I'm at. I have a great set with issues that can be almost completely mitigated with selective use of CinemaSmooth. Of course, movies aren't 100% light or 100% dark but usually the visual style is consistent so this way works fairly well. Now, if I was able to spot judder I'd have to watch only dark movies but fortunately I'm not.
Oh, and yes, I suppose I could contact Samsung again. To be honest, after two replacements already I'm kind of tired of dealing with it. It's too time-consuming and there's no doubt at all that the so-called panel lottery is real, at least with Samsung. (Not sure about the other brands.) I know what I have but not what I'd get...