"Hmm, #KiCad pcb editor is awfully sluggish on this laptop."
"Oh right, this laptop has a bajillion pixels (288 DPI)"
*turns anti-aliasing down from "high-quality" to "fast"*
no more lag, no perceptible visual difference

actually, no perceptible difference if I turn the anti-aliasing totally off, unless I get my face right up to the screen

Having a setting (and making it the default) to have it adjust anti-aliasing dynamically based on detected DPI and/or detected lag would be cool. Better initial UX without having to fiddle with settings.

That said, the existing button to auto-detect DPI for measurements gives me... not-quite-what-I-expect results.