I have noticed general app lag when doing pretty much anything in Aseprite, pretty sure the lag wasn't present in earlier versions.
Dragging windows is sluggish and sometimes lags behind, but what concerns me the most is that when drawing something on a canvas and frequently using Undo, it becomes really sluggish and slow, after that pretty much everything lags behind for a while and it's really annoying.

Haven't been able to test it on a different OS than linux, but if anyone has or had similar issues, would be nice to share them here.

Edit: after working in a 128x128 canvas for a tilemap, simply dragging around the canvas becomes super laggy as well and it's annoying.