I recently walked the full length of the canal from Liverpool to Leeds over a period of 9 days (12th. to 20th June,2010).
I needed a map in order to locate stopping points for lunch/overnight stops and this map was invaluable. Three of the places which I had earmarked as stopping points for lunch were no more, alas, but thanks to the map, I was able to find alternatives quickly. The famed 'Hole in the Wall' at Foulbridge (Mentioned in the map) is no more - it is now a 'Hole in the Ground' haveing been demolished. Sad.
If you are thinking of doing the full walk, or just a section, then this map is essential. All the bridges, locks and tunnels are named and numbered so in the event of an emergency, you know exactly where you are and can summon help quickly.
All in all, an essential piece of kit and well worth the purchase price.