other than super terrible battery life, (4K and OLED, combined.. *_*) it is an "EXTRA" high-gloss coating, much higher gloss coating than standard, IPS glossy-reflective.
NITS won't be an issue as far as brightness outside, bugs may even probably want to even land on its lush display.
depends on how much shade you can give the OLED screen. an anti-reflective coating will help tremendously and the display will still visually look better than a quality IPS screen.
can you live and sleep without it? probably.
I've seen a Sony 940e (non-OLED, 75-inch, $4,000 retail at release) TV that can process different levels of HDR and offers a high customization of motion-blur levels.
When compared to an OLED TV, it's sometimes hard to tell the stark differences from afar between the two.
However, when comparing to a low-end Vizio, anything will look better..
if you're going 4K and you have the option for OLED, get the OLED. it's not like the laptop will last forever, anyway. enjoy what's available.
considering the options out there and mobility factors, i'd instead opt for a high-end IPS touch with extra tight 1:1-ratio-pixel pitch and decently bright NITS.
we're talking 2020 here, if your internal 4TB SSD is loaded with locally stored & offline, fresh 4K content, then go with the OLED..