I've used Kinko's for this in the past when I lived close to one. Unfortunately, it's kind of a long drive from where I live now, so it's not the most economical solution. Thanks for reminding me, though; I had forgotten about that as an emergency option.
The problem I run into when trying to use a different image editor, like Gimp, is that sometimes my clients send me PSDs with complicated photoshop layer masks/filters that come across wrong/weird in anything else.
