I compared ImageOptim and PNGSquash and PNGSquash made both files about 4KB smaller than ImageOptim did, both were using the highest optimization settings for smallest file size.
I had PNGOUT installed too.
I like PNGSquash and I think I'll use it to optimize all my images. The only features I'd like included that ImageOptim does have are the ability to drag a folder into the window, so I don't have to pick out the pngs from a project I'm working on, and an auto-updater. Growl support would be nice as well.
Also, I agree with weaksauce's comment, you could just have the user download and install pngout separately, just tell them to drag it to /usr/bin and look in that folder for it, that's the usual location for it anyways. ImageOptim does this already.
I like PNGSquash and I think I'll use it to optimize all my images. The only features I'd like included that ImageOptim does have are the ability to drag a folder into the window, so I don't have to pick out the pngs from a project I'm working on, and an auto-updater. Growl support would be nice as well.
For an auto-updater framework I like Sparkle a lot: http://sparkle.andymatuschak.org/
Also, I agree with weaksauce's comment, you could just have the user download and install pngout separately, just tell them to drag it to /usr/bin and look in that folder for it, that's the usual location for it anyways. ImageOptim does this already.