I tried Photoshop once... I didn't find it any better than the GIMP... Of course, first impressions mean little with advanced programs, but I've never had any trouble with the GIMP, aside from its learning curve, which really isn't that different from Photoshop.
I would actually recommend Paint.NET for quick, simple edits, since it's easier to learn and use, while being faster to start up, and the GIMP for the powerful edits where you need lots of features, etc.