I love this medium. Its just a black line but you can suggest so much by varying the weight and density of that line. seeing how much one can do with so little is a great challenge.
Sketchbook Pro has a number of brushes that can be used as is or tweaked to resemble a line made with a nib pen or inking brush.. The pencil tool can also be used as an ink brush as long as your properties for the canvas is set to a high resolution.
There is a brush I used for the drawing of the woman on the left that I honestly can't remember if it came with the program or it was one of the many tweaks I made as I went along. It resembles a line made with a brush with split hairs. The resulting image looks like either a dry point etching or a dry brush drawing.