nyaa, the Raspberry Pi 400 is everything I personally want out of a computer, I think. 
Low heat, energy efficient, tiny and portable, replaceable & upgradable storage space, with no inaccessible components that die after 4 years (like rechargable batteries)... 
Can play some game decently well.
Maan. If Godot Engine had an officially supported ARM build for it, I might even make that into my main development laptop. 
And use it with the most energy efficient lowest-brightness monitor I can find, nya.
The downsides to using an ARM system on a chip as your main computer are nearly identical to the downsides of using Linux as your only OS:
It doesn't play all those super cool overly detailed fancy newfangled Unreal Engine 4 videogames that were only released for Windows 10.
Just, with the additional caveat that you can't "shoehorn it to work anyway" using Proton or whatever, because it's a low-power ARM device that wouldn't be able to run it decently on even the lowest settings that game offers either, even if you tried.
As long as it runs graphically-simple games like ADOM and Cataclysm:DDA, who cares about missing out on all the fancy pictures?
...good grief. So you can handle low-polygon 3D on a Pi?
...so, if you add in a couple of accelerometers, a pair of very small screens, and maybe a GPS system, it might even be possible to get a pair of entirely self-contained low-polygon-count VR goggles?
@ccc It seems plausible, yes. It doesn't need a pair of screens, just one wide screen split in half by a separator, ala Google Cardboard.
It might require some incredible optimization to get a framerate that doesn't immediately induce sickness though. Frustum culling, possibly skipping the fish eye rendering in favor of a limited fov, ...
But I think it could happen.
@ccc Yeah, but wow, it's come to the point now where the Pi itself actually does have a dedicated integrated GPU of some kind, capable of handling OpenGL ES 3.0 specification at release.
I don't know the exact benchmark details, but just having a GPU that can handle that shader level is already more than enough power to run basically anything meaningful.
2D? Doesn't choke, even with all kinds of layered fancy lighting effects and a full desktop environment! 3D? Just limit your polygons and textures to reasonably low specs and it's probably fine.