The situation is much better than you think. Yes I think it would help if you had a large scale map to get some sense of the whole. Beyond that, there is now the fietsrouteplanner, the online routeplanner for cyclists. See
http://www.fietsersb...tsroute-planner
Unfortunately the interface is still only in Dutch, but I guess you should be able to work it out. The green version uses the two existing network systems: the network of signposted long distance bike routes (LF routes) and the nodal points system (knooppuntenroutes) where you can build your route going from one numbered nodal point to another. The nodal points are numbered and there are notice boards with detailed maps. The only hard part is getting to a starting point (railway stations area good bet). The green routeplanner combines the information of these two systems to design a route for you. The red one also uses other roads, and has settings for "fast", "nature" etc. I have only tried the green planner. The green planner is the product of many cyclists who have traversed the country to decide on the best roads to take. The red one looks like a computer generated model. As of this moment, there are still a few parts of the country where the nodal point system is not yet complete, and where the red planner does not work at all (planned completion October 2011).
I think if you have some idea of where you want to go, and do not want to use your internet smartphone all the time, you could prepare most of what you intend to do beforehand, and print the route maps. Locally you can always stray away from your planned route by using the nodal points.
Enjoy, the weather has been great thus far,
Willem