Color spaces is the big one—such as Lab and CMYK. I’d also count 16-bit support, since GIMP’s 16-bit support isn’t very good. The list gets much, much longer w

Color spaces is the big one—such as Lab and CMYK. I’d also count 16-bit support, since GIMP’s 16-bit support isn’t very good. The list gets much, much longer when you compare GIMP to newer versions of Photoshop, like Photoshop 5 from 1998. Photoshop 5 completely blows GIMP out of the water in terms of both features and usability, it’s a complete joke. I don’t use Photoshop any more, and I’ve exited the Adobe ecosystem, but once you’ve used tools like Photoshop, using GIMP feels like swapping your nice DSLR for an old point-and-shoot. Sure, you’re saving a lot of money, but you are constantly reminded that you developed a bunch of skills that you can’t use any more.