It is a different paradigm. I learned on GIMP and when I have to use Photoshop I feel like an absolute idiot. At the end of the day, Photoshop can probably do more, but GIMP has been sufficient for all of my needs.

I might as well mention that Krita is worth looking into as well. It's more of a drawing program than a photo manipulation program, but there's a lot of overlap and people seem to like it.