I tested out InkScape at lunch today, to see if it was any good at inking. Actually, that's a lie, because i know it is, as I've used it previously - the only problem I had with it was that it could be difficult to use... Not any more.
Two additional features have been added to the latest release (0.46 at the time of writing) which make inking easier, as well as some additional options. The first is changes to the calligraphy tool, which now has a mass option - this basically slows down your drawing movement, which helps promote a smoother line. The second is the tweak paths tool, which allows you to push and pull paths in a magnet like fashion - great for fixing small inking errors.
One other thing - the preferences are better. I used to use the "simplify paths" option, which removes extra nodes from a shape, but I always found this was too vigourous. There is now a preference setting which controls this, making this option less of a hit and miss affair than it used to be.
For best results, set calligraphy tool mass to 0.10, simplify to 0.0030, and use a graphics tablet. The above picture was drawn using only a mouse - the graphics tablet makes it look even better!