Here's a few...
* Even though there is tons of extra swap space, running too many apps at once causes the entire system to become unresponsive for ~20s at a time. Granted, I am using older hardware, but there should be some minimal amount of responsiveness allocated to indicate the system isn't just totally dead.
* Wifi GUI Gnome utility often ceases working and requires wifi to be turned off and on again. I got so fed up with this I just wrote a command to set Wifi to my credentials, and even then, I have to unplug/replug the wifi dongle frequently to get it to re-register with the system. On Arch Linux, this GUI utility doesn't even work at all. This has happened with multiple different makes of dongles.
* When I was using Ubuntu for work purposes (and Python / node / Docker stack), it would frequently run out of file descriptors. There was no solution other than to restart.
* Last night I started to encounter an issue where Ctrl-X would cut text successfully, but when I go to paste it, it will not be there. Possibly a bug with VSCode, not sure yet, but I haven't encountered it running VSCode on Mac at all.
* Something about programs being interrupted by context switches to other programs that are using large slices of CPU time leads to input being misinterpreted. If I am running a Rust compilation in one window, typing `hello` into an adjacent terminal window might show up as `hellllllllllllllllllllllllllllllllllllllo`. This happens in a wide variety of applications. I suspect the problem has to do with input library routines not receiving real time priority, or something like that. Weirdly enough, I saw the same issue on FreeBSD.