Ok so first bear in mind I'm not as technically minded as some in this thread but do know the basics. I may be a little biase as well as my ks8000 developed faults twice in a two year period.
So it was the B8 65 inch I've upgraded to (no way could I go smaller than my old tv) for £2000. First up the build quality appears to be really good. No glue back to be found and the tv is so thin. Maybe the thickness of my S7 edge for most of it. It does make wall mounting the unit really unnerving though lol. Due to height differences using the same stand I had to mount it THREE times as well to get it the same level as my KS8000.
The picture is AMAZING. This is my first OLED but I've never seen a better picture at home or in the cinema. The blacks as so good, for certain things it's like there an image on the tv screen even though it looks like the tv is off

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One thing I really like over the KS8000 is it seems alot easier to see the effects of options as your adjusting them on the fly. Sharpness, contrast, colour temp etc. In game mode you can literally adjust the colour temp in increments on 1 rather than 4 or 5 present (though that's present on other viewing modes).
The wand remote is really nice feature, not just a gimmick and is my preferred way to control the tv. (Like using a mouse really).
Sharpness seems alot less aggressive on this. Again I'm not an expert but say 0-30 I noticed no artefacts but also didn't notice that much of an improvement either. Over all of say it's a lot more restrained.
The picture out of the box is so good and very accurate to my eyes. You could very easily modify the only "incorrect" setting the colour temp from cool to warm and call it a day.
Moving on to Hdr again I noticed a huge improvement. You don't really notice that the peak brightness isn't as high because the black detail is so good. You could probably notice certain elements aren't quite as bright if you had the images side by side HOWEVER I feel the benefits if pure blacks and image clarity far out weighs this.
I haven't had chance to fully test HDR games in depth yet, but Horizon at night (in game) wow it looked soooo much better. Where's normally you could argue it's a 20-30% better picture during the night time scenes with stars etc it looks a multitude of times better. Tone Mapping for me makes the picture excellent no matter the individual game where's before on the KS8000 it was debatable about using DC and it didn't get on with some games (like final fantasy 15).
No issues with input lag to me. Feels as responsive to me as the KS800 but I'm not highly susceptible to it in the first place. I believe it's about 22ms in game mode.
Another benefit is no clouding or light bleed etc. You really do notice it's absence.
Positives.. a MUCH better picture both in SD and HDR, build quality vastly better (so far), great OS.
Downside... price although justified realitevly expensive & HDR peak brightness (with it been OLED).
In summery in this layman's opinion it comes HIGHLY recommended and is a substantial upgrade for both movies and games. I think the best praise I can give is that I could never go back now to LED after OLED, the improvements are just too vast across the board with the small niggle of peak brightness that is vastly outweighed by all the benefits and the pure black levels.