I tried using Krita several times, mostly because of its animation features, to replace my current GIMP + a custom set of animation plugins setup. But it's always unbearably slow on my computer for some reason. By slow I mean lag when updating the canvas - there's a very noticeable delay between moving the stylus with my hand (I'm using a Wacom Cintiq) and when the line appears on the screen.
It's probably something specific about my hardware and/or Debian system (I've been trying Krita's AppImage downloads). GIMP on the other hand doesn't have any problems with it.