I said rugged and featureless but with the need to stay on a particular course. Featureless (no mountains or mountains hidden by trees or covered by clouds or obscured by fog) means you can't triangulate very well with the compass and rugged means you can't hold a straight line, so you are very likely to walk in circles. Furthermore, the ruggedness may not be evident on the map. A 10 foot cliff, for example, is a difficult obstacle, but doesn't show up on topo maps. Karst country is full of such cliffs. In swampy areas, the natural tendency is to stick to the dry ground, but that may take you way off course, and you may have a devil of a time getting back on course, especially if the trail is not well-marked. Snow travel is another classic case where topo maps are next to useless. Bike tourists seldom or never encounter these situations though backpackers do.

Obviously, people got around with GPS or even topo maps in the old days in rugged and featureless terrain. But they did it the hard way, by trial and error, backtracking when necessary and trying another path. Also, outdoors people were much more skilled at navigating by dead reckoning in the old days and that art has mostly been lost. I'm not anti-technology by any means. But I'm not a technology-fetishist either. If something is truly useful and doesn't add too much weight or expense or hassle factor, I'm open to it.

And I'm not being hostile. I have tried mapping GPS's. They weigh extra, and I'm a gram weenie when I'm backpacking (not when bike touring) which is why I prefer lighter weight non-mapping GPS for that activity. There are plenty of intersections on some of the trails I've hiked, probably just as many intersections as with bike touring. Some of these intersections are labelled, so I don't need to refer to my map, much less my GPS. Sometimes the intersections are not labelled, or there are more paths than shown on the map, or I have to cut cross-country for some reason (avoid a big patch of ice, trail has been obliterated by landslide, etc) and then a map of some sort assisted by GPS comes in very handy.

The OP of this thread asked for opinions about using a mapping GPS or netbook or tablet versus paper maps for bike touring. It's a topic I'm interested in, because I'm considering buying a tablet computer or smartphone with much larger screen than my current phone at some point, and possibly using that tablet/smartphone for navigation on bike tours. If I seem to be combative in this forum, it's because I'm actually not closed-minded and am open to new perspectives, but I am very much concerned about making the best decision. I don't want to buy expensive devices and then later regret the decision. So far, nothing I've read has shaken my belief that: (a) some sort of paper maps should always be carried to get an overview of the situation and serve as a backup if and when the electronics fails; (b) a tablet (or large screen smartphone) would be a much better addition to a bike touring gear list than a mapping GPS (for those who can't or don't want to carry both).