We use an acer N35 with memory Map,buying this was the reason for starting in Geocaching.
The battery life was a problem when we were out all day walking but bought a battery extender which helps no end,a strip of velcro helps attach it to the back.
Sticking it it map pocket gets over the waterproofing and back up data before setting of as it crashes now and again,restoring only takes 2 mins