Re: GARMIN GPSMAP-276C anyone use one for the boat?
I bought my 276C for the boat and later added the auto package. I have been very happy with it in both applications.
I use Mapsource's US Recreational Lakes for marine use and City Navigator V8 for road use.
Additional firmware can be added by preprogarammed card or loaded from a CD/DVD. I use the CDs and have 2 cards that I could program, but find that one 256M card holds all the maps, etc. that I want on one trip.
The later versions have added features but, of course, you will have to pay more for them.