I've owned a KK S61 MkII for a couple of years now, it is my primary MIDI controller and it gets a lot of use on the OB-X8 desktop module specifically, since many of my other analogs have a keybed.
My initial reaction was that I may need to upgrade just to get poly AT, but then I saw Loopops video about the MkIII and realized I might be making some tradeoffs I regret... Maschine integration would be missed in my case -- being able to identify which sound via the key light coloring. He also said the AT response is "steppy" compared to the MkII, which is a bit concerning. I was also a bit disappointed to see they didn't make room for longer titles on the knobs in MIDI mode, that would have been useful, but of course that is no worse or better than the MkII. He points out an annoyance I noticed right away -- the values of each knob are no longer displayed until you touch them. Ugh.
Now most of that can probably be addressed with firmware upgrades, let's hope they do. But items like the knob title length could have been addressed in firmware on the MkII as well and it never happened, so because it can doesn't mean it will.
On the other side of the coin, there were many times I had considered getting a Hydrasynth keyboard version to replace my desktop, just for the benefit of poly AT. Now at least I have an option to get a KK MkIII 49 key version at a much lower expense, and I could then decide how important poly AT is to me in the big scheme of things. For now at least though, I'll be sticking with my MkII.