If you're looking for a full-featured image editor at a relatively low price, Pixelmator fills the bill nicely. Sporting a smooth Mac-friendly interface, Pixelmator offers a layout much like Adobe Photoshop with separate toolbars offering standard selector and paint brush type tools, a color-picker, a layer manager, and a brush picker with large array of options, from "follow direction" to multiple jitter settings. Pixelmator also has support for Adobe Photoshop brushes.
Also like Photoshop, Pixelmator comes with all the image manipulation tools you might need for adjusting color, saturation, brightness and contrast, and many more. If you want to add effects to your images, you can pick from several different common filters like distortion, blur, sharpen, halftone, and stylize, along with more esoteric filters like clouds and noise. Essentially, Pixelmator gives you a lot of the same tools, effects, filters, and capabilities (like save for Web and trim) that you would find in Photoshop, though you won't find many of Photoshop's more advanced tools.
Perhaps the biggest difference most users with above average image editing needs will notice is Pixelmator's price ($59). It's important to note the demo version watermarks all your images, but once you see the amount of features this app has, you probably won't mind paying for all that functionality.
Pixelmator is an image editor for Mac OS X that allows you to create, edit, and enhance your images. Interface designed for work with images, layers-based image editing, use over 20 tools for selecting, crop, painting, retouching, typing, measuring, and navigation. Use over 15 color correction tools, use over 50 filters, adjust image size and resolution. Transform images, layers or selections using transform tools, fill and stroke images, layers or selections, photo browser offers quick access to iPhoto Library, events, albums, smart albums, and pictures folder. Use your iSight camera to add pictures to your compositions. Includes automator actions for converting, resizing, enhancing, adding special effects, and transforming images. Image processing is powered by core image and open GL.
What's new in this version:
Adds New Drawing, Retouching and Smudge Tools, Content-Aware Fill, and Support for OS X Lion.