Paint.NET is also nice. Probably not as sophisticated as GIMP or PS, but still very good, especially for simpler tasks.
Personally I would only use GIMP if I had no other choice and serious work to do. Since neither of those is the case, I don't generally use it. Even a lot of its supporters will readily admit it's no Photoshop. I have used it in the past and it is very good for what it is, but "free" is definitely the most I would pay for it.