Battery life, display scaling, sleep & wake up issues, trackpad gestures, sound output, GPU-accelerated video playback... Just to name a couple of problems I hope not to encounter every time I decide to give Linux another chance, but I still do.
To fix them, you need to run some arcane commands, edit some config files, compile your own kernel, ... I don't know. I'll have something that "just works". I'll keep using Linux headless on a server, where it really shines.