Photoshop is actually the tool of choice amoung 2D artists that I know. A good friend of mine does album covers for bands in Hollywood.
Here is the process he uses:
1) draws picture on paper using black lines
2) scans the picture in
3) uses pen tools to create selection paths for the different parts of the drawing
4) using selection paths, 'inks' the lines to the proper width on a new layer
5) creates a layer under the line layer
6) uses the selection paths again to paint (using airbrush tool and his Wacom pen) the various areas of the image
7) deletes the background, flattens the image.
although this is a lengthy process, his work is incredible. here is his stuff:
http://www.dirtywett.com/home.html
-= i only do what my rice krispies tell me to do =-