There's been discussion on solar charging while riding, and it seems in many cases it's not possible to keep the panel properly oriented towards sun for really effective charging. If you want guaranteed charging, look into some of the dynohub based systems that are available. If you search this site, you'll also find a DIY solution by member n4zou for such system. Often it's easier to just ask for a permission to charge batteries while having a break at a cafe/restaurant, for example.

I don't trust the GPS alone when touring, I always bring paper maps as well. Most often the GPS is in the handlebar bag, as a backup and data logger for trip diaries after the tour. For trip planning, I cannot get by with the small screen alone, so I use paper maps for that too. My other hobby is sea kayak touring, there the GPS gives me speed, distance, heading and location info. Still, it's an electronic gizmo and many things can go wrong, so I make sure I know my location on the sea chart as well. GPS fail has quickly become one of the most common reasons for recreational boaters' distress calls around here.

--J