GraphicConverter is an awesome app. I've used it for many, many years, and it's the cornerstone of my graphic workflow. That praise aside, it has its quirks and functional holes (like there's no batch action to change the image label, a useful side-effect to show that you've processed an image).

But the biggest issue that I have with GraphicConverter is its recent bugs, since 6.0.2 + Leopard on PPC. Bugs in adding text, dealing with alpha channels, and selecting a portion of an image. Dealing with the developer is an exercise in frustration; I've met with Thorsten many times at MacWorld San Francisco, and his English is too fluent to account for the flakey and delayed responses to bug reports and feature requests. Until I can use 6.0.5 or later for more a few minutes without finding a show-stopping bug is the day I upgrade from 6.0.1.

Still, I've checked out the competition, like Pixelmator and Photoshop (which I use for heavy-duty levels), and GraphicConverter has a very comfortable combination of features. (I also echo previous posters in wishing that Sparkle would be used for in-application updates, that manuals would be offered as an optional download, etc.)