I tried to participate in the net last night, but reception faded before my turn came up - sorry...
I have a Garmin 2730, which does 3-D street mapping, voice prompts, XM radio, weather, Stock quotes, etc... so although it is not really designed for off-road navigation, it does have an amazing number of the common trails in it, and you can input lat/lon coordinates.
To help with more specific topo info, and to have a larger, more readable daytime screen, I added a Lowrance GlobalMap Baja 540c. I assumed, since most race teams use it, it would be the end-all for off road navigation. Well, the screen is awesome, but the controls / software are older technology than most current GPS units. If you are plotting your own stuff, it's great - if you are dependant on the MapCreate Topo info, well, it's OK. And the Garmin is more accurate, IMO.
So, for reasons beyond just GPS, (repair manuals, operating manuals, pictures, etc) I added a Toughbook laptop to the mix. It runs Microsoft Streets and Trips 2009 (great for in town, not as good as the Garmin, not for off-road, but it was free to me

) and National Geographic Topo. The NG Topo maps are great - but so far, I am not thrilled with the software interface; it's not intuitive, it seems to stop randomly when in the tracking mode, and many features stop while using other features; again, it seems like older technology to me. THey do have some very cool features, including a 3-D flyover mode to check out a trail or area before you drive it. I only wish this could be used while in motion or while tracking. All in all, I need to spend more time working with these programs, but the documentation is awful at best, and I'm not big on constantly hitting the "Help" key. So, maybe these programs will work better as I use them more often.
I use GPSGate (thanks, DaveK) to allow multiple GPS programs to run on the screen at the same time - it works great.
So, I've got many sources, and none that I feel really do the job 100%...maybe a satellite link with Google Earth is the next step (when the economy improves

).
I hear alot about Ozi Explorer, but I would like more info on how it works before being disappointed again - what maps work with it's interface ?