Avalanche941,
The GIMP has many more features and is more mature, while Paint.NET has more of a Windows-like interface (although the latest verions of The GIMP is more Windows-like than earlier versions). Paint.NET is good for quick simple tasks (such as removing a background colour), while The GIMP is better for more complex work.
Rasheed,
Staying off-topic:
Rasheed wrote:Alas I haven't got many draw programs (vector graphics).
You probably already know about/have this one, but
Expression 3.3 for Mac (and Windows) is still available. Fairly large download, about 60 MB, but free (marked as beta/test, but fully functional and non-expiring). You have to jump through the survey/registration hoops before downloading.
Excellent formerly-commercial vector graphics program, bought out by Microsoft and being redeveloped for Windows Vista (no Mac version). Fantastic vector brushes. Have a look at the Gallery linked from that page.
In my opinion (not everyone will agree, I'm sure), the Expression 3.3 interface is not quite as usable as the Xara drawing products, but it includes more features.
Go through the Studio E3 tutorials (under Additional Resources on that web page) and the tutorials in the PDF manual to get a decent grip on the interface.
If you use plain (PS) lines instead of brushes or gradient lines, and stick to plain fills, it exports to Moho very nicely, or it can be used to produce bitmaps for backgrounds, character parts, etc.
Speaking of Xara, keep an eye on
http://www.xaraxtreme.org/, as a Mac version of the latest commercial Xara Xtreme is on the way as Open Source.
Regards, Myles.