DeLorme PN-40
I have been using a PN40 for about 2 months now.
Originally I thought I'd sell my Garmin eTrex Vista HCX but now I am glad I did not.
The PN40 needs more polish. (That's a very short review isn't it.)
Software and maps for the PN40
Topo 7.0
it appears to be very inaccurate.
Street Atlas 2009
maybe it's accurate, but forget it, you can't transfer SA data into the PN40.
XMap 6.2
I have it on order
USB to Serial
There is a program on the DeLorme site that you can use to take the live data coming in over USB and fan it out as one or more NMEA serial data streams. This means you can feed several client programs running on a Windows desktop machine at the same time. It also means you might not have to do anything at all with the binary protocol if you just want to get NMEA position data.
Binary protocol
The "DeLBin" (DeLorme Binary) Protocol spec is downloadable from the DeLorme forums as a PDF.
I am looking at trying to write some software for the device. To do that I will probably need to look at USB packets using a USB monitor.
ArcMap support
You can use Topo 7 to transfer track(s) from the PN40 to a desktop, then in the Draw tab you can export the tracks as GPX data. Then you can convert the GPX files to ESRI shapefiles using DNR Garmin.
This is so cumbersome! So one project I have in mind is an ArcMap extension that allows direct import of tracks from the PN40 into ArcMap.
Of course support for waypoints and routes would also be nice.