iDavid, I used mappero for hiking. It's fantastic! You can preload openstreetmap for any area or route. For some places, openstreetmap has better mapping of hiking routes than any other source. I loaded the whole of Tenerife onto my N900 and had some great hiking adventures. It can also preload other tiles based on openstreetmap, such as hike bike map or open cycle map.

Here's a tip: the pixels on the N900 are quite small, and some text on openstreet map can be hard to read. So I preload only the even-numbered zoom levels (6, 8, 10 and 12). In the field, if I zoom to an odd-numbered zoom level, the N900 will scale up the map and the text becomes very easy to read.