Purchased 2 secondhand, as it has a built in GPS I have installed Memory Map on it and load the relevant area maps on it. Geocaches are marked on the maps using LordElphs icons which are in turn linked to text files containing the cache details, hint and the last 5 logs.
The only other program that I installed for gecaching is Multicalc (review to follow) as all of the cache note text files are generated by Geocache Log (review to follow).

As the GPS chipset is a SiRFstarIII satellite lock is very quick even when under tree cover.

As with all Windows Mobile based PDAs there is a Notes function that allows voice recordings to be made and we use this fuction to make verbal notes of what we enter into the log books, what we swap and TBs?Coins in and out. These notes can then be used later when we log our finds on GC.com.

Battery life is between 3 and 4 hours depending on use but we have a PowerMonkey as backup.

The screen visibility is good but in the bright sun requires some shading. Reasonably rugged but is not waterproof and therefore needs to be kept in a waterproof case if the weather is anything other than dry.

By using the combination of the GPS, Memory Map, text files, Multicalc and the voice recording function we can be paperless for our geocaching.

Any Windows Mobile based PDA with a built in GPS should be able to carry out the same functions.