Models take a very long time to load. My game installation is about 15Gb, and even in areas where I have downloaded the majority of the assets there will be long loading times and significant frame drops when loading in. These things rectify themselves after a few seconds, but it's still annoying.

The game window will go completely black when fullscreened and not focused, but it's not particularly obtrusive.

Running under Wine or Proton with the desktop version (not installed through Steam) presents significant input bugs. Sometimes the keyboard would not be recognised, and the mouse in normal gameplay would be unusably sensitive. This seems to be resolved with the Steam version.

Running Wizard101 under Wine OR Proton using lutris, regardless of the options used, resulted in significant hitches, FPS drops, and specific bugs, most notably that attempting to orbit my character using M1 was impossible since the input seemed to accelerate and zip around.

Transferring the game files over to a Steam installation, and using the same version of Proton, along with using the Wine3D launch option, fixes these issues almost entirely. The orbiting is possible again, FPS improves significantly (although it is still unusually prone to dropping in populated or graphically complicated areas), but the hitching when enchanting spells and opening menus is still present.

On the desktop version, installed through Lutris, the game would crash every 90-120 minutes. I haven't played long enough on the Steam version to know if this is resolved.