I'd thought for a while about writing a Cocoa-y Photoshop replacement, sort of like what I did on Pixen, but then I realized software like that takes years and years to build up a large enough feature base (patience I don't have). Even if Apple started right now, it'd be quite a while until they had a similar number of features. It's hard to compete with a decade of work from that many programmers. Of course, one could say the same thing about Windows, and Apple's competing with that just fine.