Ewan. Satnav is handy for several reasons. It gives you accurate A-Z mapping of a town or city you may have never been to before. It gives you the ability to organise diversions on the fly without having to park up and get out a map. It also gives you information about things like cashpoints, food outlets etc; that you wouldn't have to hand otherwise. I have both a satnav and a road atlas, and I plan any long route prior to setting off. However it's always good to have options.
As for the can't read, I spent two years doing air cartography :)