Just earlier this year, the Dailide brothers from London started off coding a new application for image editing, based on libraries provided by the OS X system and Open Source, utilizing the Mac’s video card for processing image operations. Pixelmator has tons of features to offer, making the new core-image-app a possible alternative to Photoshop. You can play around with layers, use Apple’s Automator for recurring tasks. The software supports iSight cameras and iPhoto and has a wonderful, full-screen-aware GUI. It even opens Photoshop-files including layers, though seems to lack support for the most common raw-files from Canon and Nikon, i.e. .cr2 and .nef. Probably this will be included in a later release. Version 1.0 of this Universal Binary is announced for late June at only 59,- $.
Check some press releases I found with a quick Google search: Macnews.de, MacObserver.com or over at Digg.com.