It's running ChromeOS with the Linux dev system installed. I did last year's Advent of Code in Clojure on this device, including some airplane trips. (I didn't solve every puzzle, but the limitation on the ones I didn't get was me, not the Chromebook. It runs Emacs, cider, and the Clojure REPL just fine.)

I'm typing on it right now and it's fine for casual use. (It gets a fair amount of weekend use because I neither want to undock my work laptop nor carry around something that large, expensive, and heavy.)

Would I run it as my only computer if $500 wouldn't pressure my family finances? Probably not. If my choice was between this and nothing, that's an even easier choice.

The bottleneck is usually RAM. It looks like his device has 4GB, which is similar to what a cell phone has.

It doesn't take much manufacturer-supplied bloatware, bad drivers, or background processes to use up that much RAM but a Chromebook is just the kernel and Chrome, so you get a lot of bang for your buck.