Alright, all - just picked up a new Switch at Target this evening (they just got them in today).
First things first - I don't see (with my naked eyes) any difference in brightness between my launch system and this new one. I suspect there may be variances between systems, here.
HOWEVER, the color temperature difference is HUGE. The new Switch is night and day much more neutral/natural than the OG Switch, and this is something that's obvious in everything. Even blacks/greys in the menus look miles better due to the temperature shifting toward the neutral. I wouldn't be surprised if this is incredibly close to D65K.
I need to see how warm the new Switch gets when I get to gaming with it, but other than that, it's a Nintendo Switch, with better battery life, and a much more accurate display temperature.