My favorite bug family, that somehow to sneak in every time, is how their react frontend (or whatever the store runs) manages to semi-crash and the controller inputs are no longer recognized.
I kind of hope at least they'll fix such issues permanently before the steam machine release.
That is the bane of my existence. Steam's UI is so slow to react due to its web roots, that I feel like people must be insane to think that Steam is somehow this great app. It's terrible.
I shop on GOG.