How is the feature parity?

As far as I can tell, they copied nearly every tool and menu and their behavior one for one. I'm not an illustrator so I can't tell how well they copied brush behavior for painting, but as far as editing goes, this does almost everything. One noticeable omission that I could find is lack of frame by frame animation and gif export.

I pirated photoshop when I was 12 and kept using that for image editing my entire life. The clone feels completely familiar and does exactly what my muscle memory expects photoshop to do.

Except when it turns out that some random features don't work as expected it pisses me off enormously as it breaks the whole promise of the clone.

Give it some time. There is a whole community right now hunting edge cases and submitting and merging pull requests.