I decided to give gimp a real go recently. Shifting my UI production from photoshop to GIMP, and not giving in to temptation, regardless of how quickly I knew I could do a certain task in PS.

There were a few headaches. For instance the half an hour spent in frustration when trying to move a layer, only to find that the tool panel had an "Affect: " followed by a small icon for the selection. I consider this expected pains, and there certainly were a few of those in photoshop as well.

One thing that I just consider lousy implementation was when trying to create a pattern and applying it to an image. I couldn't find a way to do this besides creating the pattern as an image, and saving it to the ~/.gimp/patterns/, refreshing the pattern dialogue, and applying the pattern.

Also, the destructive workflow in applying effects is archaic... even photoshop's linear (albeit dynamic) stack of adjustment layers feels old and restrictive.

I'll keep sticking with Gimp for a while longer... it can only get better, right? Still, at the moment I'd say it is far inferior to Photoshop regarding my productivity.