I have a Palm PDA on me all the time. Plus, the real digital wonder - the Holux GPSlim 240. It's so small and lightweight (~1oz) that I don't hesitate to carry it on me all the time too. It's connecting to PDA wirelessly by Bluetooth, works around 8 hours on full charge, very sensitive, accurate (SiRF III), and fast starting. The most reliable mapping software is Mapopolis. (TomTom is nicer in the car, but not for hiking or for any long trips into rural destinations). For hiking with custom made raster maps I'm using PathAway software.

The main problem was the power. Solved it by making a custom fit solar charger. It's less than 1oz and the size is like a piece of cardboard ( 3 x 4 1/2 x 1/16 inch ) folded. Produces 7V 480mA, without any hassle catching the sun just laing on the table (it's always on me too ).