The only thing that kept me on Windows on my personal machine was gaming and the Steam Deck has pretty much solved that. I've been running Kubuntu for ~10 months and can't think of anything I really miss.

That's not to say that there aren't issues (I rushed the Nvidia drivers and that resulted in a blank screen), but I'm definitely less annoyed - no more constantly trying to get rid of OneDrive only for it to re-appear, no more removing apps that I never asked for etc