You can see how John Bintz uses Inkscape for comics here - http://www.inkscape.org/screenshots/gal ... comics.png

I would say that your choice of tools all depends on the look you are going for with your comic. Almost all comics that you see in newspapers can be produced easily with Inkscape. But if you going for something a little more "three-dimensional" you may appreciate the freedom you get with a raster application such as GIMP. And you could also use both as you suggested. There really isn't a right or wrong answer, it just depends on what works best for you.

Some even use Blender on top of Inkscape and Gimp. It really depends on the style you're after. Experiment a bit and see what works for you.

Using Inkscape, is it possible to do inking stuff like this: http://www.illcraft.com/?p=13 ? Brian Denham said that he used Adobe Illustrator to ink that picture. If Inkscape can do similar thing, what tool in 0.47 should I use for the best practice? Pencil or callygraphy ?