For paint it's not bad. For comparisons as to what people can do with professional programs, it isn't good.
I'm not sure about GIMP but Photoshop has a thing called pen tool where you can trace a path around the object, and then stroke with precision. Also, you could then work with layer styles and what-not to try and create some depth in it. I'd personally recommend photoshop over GIMP too since photoshop has more potential. I believe you can get CS2 for free.