Last year, I went looking for a decent, reasonably priced alternative to image editing on OS X. I settled on Seashore, which had the right price of free. I have been using that anytime I wanted to push some pixels around, but also Preview in Leopard because it has the right amount of image editing tools (rotate, crop, and annotation) for a lot of jobs. I recommend adding the icons shown here to your Preview toolbar in Leopard.
That said, more in-depth image editing needs keep coming up. From icons, to image compositing, or what I think of as image surgery. With Seashore I can usually get these things done, but it feels like it takes longer than it should. That may be my lack or misunderstanding of the tool, but I started looking at new tools, since there has been a lot of movement in the OS X image editor space in the last last yet.
Back in February, John Gruber @ Daring Fireball linkedto Lukas Mathis extensive comparison of Pixelmator, Acorn, and DrawIt. The review is huge, and I don't have the same needs that Lukas does. He recommended Pixelmator, so I gave that a look at the time, but I wasn't sold on it, and eventually trashed it, leaving Acorn on my system with Seashore. Yesterday I had another image surgery task, and I fired up Acorn to try it on this task, and I got what I needed to do done in like 4 minutes. I think that is just under the time until you get the watermark overlaid on your image, but then I got distracted and the watermark got added, so I either had to buy Acorn or do my stuff over again. Not a huge deal, but I decided I should just settle on image editor and buy something already. So I googled, meaning to find Lukas extensive review, and instead found Jon Whipple's exhaustive comparison of the same three tools that Lukas compared. I actually didn't realize this until I wrote this paragraph to give Gruber credit for linked to the original review. Anyway, Jon recommended DrawIt, so I downloaded DrawIt Lite, which is free, to see if I liked the tool. I didn't pay enough attention in Lukas's review to realize that DrawIt has and iWork style interface, and that was very appealing since I have been spending more time lately in iWork 08.
I started trying to do in DrawIt Lite what had taken me 4 minutes in Acorn, and I couldn't figure out the flood fill tool. In Acorn this worked exactly as I expected. In DrawIt, I keep getting partial fills and weird color artifacts, so I probably didn't understand the tool well enough to make it work. When I tried undoing all the changes to the image I was working on it DrawIt, it crashed on me. I gave up, trashed it, and bought Acorn. I find it amusing that I ended up purchasing an image editing tool that neither extensive shootout recommended, but then again I am not an image editing pro or even semi-pro.