I have been watching Art Race, a Sky Arts programme, and really enjoyed the work done by Kenny Harris. He inspired me to get out my cartridge pen and play with the ink and water thing again. It is so much more restrictive than watercolour and it doesn’t allow for errors much. Ok, so not good if you like to get things perfect but great for making you commit to what you put on the paper.
I think it is a great excercise for speeding up and honing your drawing. The addition of water softens the hardness of the ink but it is very easy to overwork.
Art Race info is at http://www.skyarts.co.uk/art-design/article/art-race/