WARNING!!! - Be careful around nitrogen. The gas itself is harmless. It's the fact it displaces oxygen in a room that can cause you to pass out and physically injure yourself from a fall. At worst, too much and you might not ever wake up again! Unlike holding your breath where the buildup of CO2 makes you want to breath for more air, breathing nitrogen goes unnoticed until you pass out.
So yeah, use this in a well ventilated area or preferably outside.
If any of the surfaces get below the 'dewpoint' temperature then moisture will start to come out of the air. I'm sure this is considered - else your case starts to resemble an old fridge freezer caked with ice. Or a nice fog with rain.
Well if they design all the components with multiple thermal protection layers from reaction of ambient room and case temp (and humidity), any condensation and/or O2 sucking will be a non-issue. Of course doing this would make the tubes and fittings larger. This is probably what they are working on the most and why a consumer AIO version won't be released anytime soon.
Regarding getting light headed around NO2 (aka laughing gas dentists use), as a licensed pilot, we are trained to recognize the effects of hypoxia from a lack of oxygen. If you start getting fuzzy headed and can't think clearly, you put on the standby O2 mask like yesterday. Warning labels should be on any NO2 consumer AIO product of this happening, especially in smaller rooms with not much ventilation. As CO2 is heavier than either O2 or NO2, buying a CO2 detector and placing it in a low position near where are you sitting would help give an early warning, but it's not fool proof.
you might have extremely low temps, but even with a system like this, its not really viable for consumers, you just vent N2 gas off and once that tank is empty your buying another tank of LN2, those are about $1000 for a 50liter tank.
it might not run as cold, and have a higher initial cost (especially per liter price) but id much rather have two-phase immersion cooling gaming PC's, yeah it costs about $1500-$2000 to fill something the size of a gaming PC with Novec fluid, but you dont have to replace it, and while your not going to be running at -100, you'll have stable 50. you wont have to worry about losing a hand to severe frostbite if you need to repair your components and it keeps the entirety of submerged components dust free, and theres not any condensation to worry about because everything is submerged in the non-conductive fluid, and its not greasy like mineral oil bath PC's