Krita is centered around digital illustration and painting. It can't really compete with Photoshop's advanced computer vision features like healing brush, quick selection tool and 3d panorama editing. But if you just need to do some color correction and light airbrushing, it can be used instead of Photoshop.

Also, if you can put up with the UI for the plugin, the G'MIC filters contain some cool stuff. You can do frequency separation and content aware fill.