I agree I have a Treo 650(palmOS) with GeoNiche and TomTOm on it.
I use GSAK (Geocaching Swiss Army Knife) to convert the LOC or GPX files into:
- POIs (Points of interst) that TomTom can read
And
- palm database files that GeoNiche can read.......
GeoNiche is a great Navigator and Cache Magement tool.... TomTom is an amazing Street Navigation tool.
PPC owners may/maynot have more software options but i am happy with the above mentioned tools......