Only major bug I noticed with Steam under Wayland was that the Steam Chat window would render at like 1fps (or at least the textbox) if all the Steam windows weren't unminimized (in other words, if you had just the Steam Friends Chat thing open, but the main Steam window minimized, it'd horribly stutter). I've noticed this under a Wayland session of gnome-shell (mutter?) probably a few weeks ago.

Otherwise I'm still under an X11 session and weirdly I've had issues of Steam just going completely unresponsive any time of day in the background for the past week or two, when it hadn't before (I am on the Steam Client beta branch, to note).

Only still using an X11 session for being able to VR, as when I last tested SteamVR under Wayland it couldn't get exclusive access to the headset or whatever.