+1 for Acorn, and also check out Retrobatch by the same developer - it's a super powerful image processing environment - the way I'd describe it is like having a visual command line dedicated to image processing (but better because it's visual and you don't have to read man pages).

Great work all around by Gus Mueller.

Thanks! Pixelmator just didn't click for me. Hotkeys were different and it felt like it operated slightly differently from old school Photoshop.

Gus has personally responded to every bit of feedback I’ve submitted, with quick turnaround for bug fixes and thoughtful engagement with suggestions.

Acorn strikes the right balance for me of simplicity vs richness of features.

I got both when they were very cheap, and I stuck with Pixelmator. It felt best for me. But ... I'm a casual user. No clever or subtle edits.