Turns out that all this time there’s been a pretty sold Photoshop alternative in the shape of Photoline v14 (another piece of German shareware … what is it with these German indie developers?). It’s a cross-platform app and its UI seems a trifle clunky in spots, but it’s very stable and its feature set is certainly in the ballpark (in fact it has some nice features that Photoshop doesn’t have). Price is €59 (about USD 90).
Oh, and Photoline launches in ~1s.
Sorry, but a half-assed image editor with a ton of Core Image filters is no match for a mature image editor with a few well chosen filters (Gaussian Blur, Noise, Clouds, etc.).