Water stones are only really practical for bench sharpening. The idea of cutting one in half and carting it around for field sharpening is utter rubbish, even if it is taught on certain courses. It can be done, but WHY would you want to?!? Diamond and ceramic stones are so much more convenient in the field.
In the capacity of bench sharpening, water stones are great. They are relatively cheap, and come in a wide range of grits, not just "Coarse, Medium and Fine".
If all you sharpen is bushcraft knives then something like the DC4 could be all you need, but if you also have chisels, planes, axes, etc, then a set of water stones will be very worth while. You can buy several grits for the cost of a ceramic bench stone too. The main down side is that they are a bit messy and don't stay flat, they need to be dressed every so often. That said, many ceramic stones aren't really flat. The bench stones are, but many pocket hones are not. I wouldn't touch one of my fine chisels with a DC4!! :yikes:
Lurch, sorry I can't give any good tips for the Lansky system. I have never even handled one :roll:. I can only think that you could need to strop the edge, that there is a wire that needs removing. I haven often had a knife that seems a bit dull after sharpening suddenly become razor like after a quick strop.