I am a new user of the Triton GPS, and here is some of my opinions on the unit.  I have the Triton 300, but have seen the other models and have read everyone's opinions on several forums.

My general impressions.

The hardware is built to be very rugged, and in that regard, I think they have done well.  The accuracy is very good, much better than the SportsTrak model that my mother has.  On a recent geocaching trip, I programmed several cache sites into both units manually.  The SportsTrak got us within a 20 foot radius of several of the caches, the Triton got me within 5 feet most of the time, even in a heavily wooded area.

The default map that the Triton 300 came with left a lot to be desired.  I might as well have had a blank screen.  The updated firmware included a better map that at least shows the highway, railroad, and river that run next to my town.  I have since found better maps of my county and have played with converting them and installing them, with some success.

The Vantage Point software looks like it has a lot of potential, but it is far from a finished product.  Unfortunately, it doesn't work under Wine or even in XP SP3 running in a VitrualBox environment with DirectX support.  This limits me to having to use my wife's computer, when I can pry her off it.

Now from my Linux developer point of view:

I have used the light+up+power button sequence to start the system in debug mode.  Once started, the system shows up as a USB storage device with label "TFAT".  I have been able to copy the entire memory contents from this, and have started experimenting with the various bits.  

There are 3 directories on the system:
APP
MAP_DATA
USER

APP contains the magellan shell and the navigator software.

MAP_DATA contains the default map, along with any uploaded maps.  Knowing this helps, as I can now generate a map and just drop it in this folder and reboot the unit to test it.

USER has several files, the most important being the user1.uds file.  This is an sqlite3 database file that is structured to contain far more information on routes, waypoints, and geocaches than the software currently allows.  I'll post an excel spreadsheet with the database map later.  Needless to say, it looks like a lot of planning went into this database, and the company is working on implementing these features.

The latest firmware for the Triton 300 (v1.88) has a bug in it that when downloading .loc files from geocaching.com and uploading them through VantagePoint, if the difficulty and terrain fields are blank, trying to look at the details of the geocache site on the triton will cause the software to enter a loop, followed by a shutdown after several minutes.  I think the software is expecting an integer value and not accepting a null value.  I'll need to test this more by comparing uploaded information with manually entered data.

I have not been successful yet in figuring out how the default communication protocol works, but it would stand to reason that it is acting as a usb network device, with VantagePoint communicating with the Magellan Shell on the gps unit, similar to a client<>server setup.

I'll post more as I continue to work with the system.