I want to emphasize just a bit more the utility of GPS touring and how it can change your approach to touring. I'd agree with NeilGunton (and who would not) and point out that there are different ways to use the routing ability of the GPS. I uploaded a complete collection of my routes out and back across Pennsyvania and I used them every day and 80% of the time that worked OK. However selecting the "right" number of waypoints can be tricky. If you're "freerouting" (i.e. going off the auto seletcted route) you have to be careful the GPS isn't routing you to a waypoint you're no longer interested in and/or is far out of your "way". Its no big deal to delete a way point or to just chose another point to route too and have the GPS just calculate you a new route. Also remember that the highway avoidance setting can involve you going the long way (sometimes very long!) between two points - somtimes that is what you want and sometimes (say at 9pm when you're tired and hungry) not. None of this you can really do on the fly while actualy biking - you're going to have to stop unless you are very dextrous (I'm not).

Did I mention that the GPS will quite happily route you up the very steepest mountain and there is nothing you can do about this? Unless you follow carefully pre laid out routes with carefull selection of waypoints and stick religously to them the auto-routing will somtimes work against you. Different folks, different strokes etc... Double did I mention for taking paper maps as well?