If you are going to use this in the car as well, I have the 855, and like the voice commands that IT responds to, while driving. Seems like a good unit, and so far is pretty solid on the road. Push a button strapped to the steering wheel and take a detour without toching the map.
Tell it to go to an address, spell the street and number and tell it to go....how can you go wrong with that???
With lots of noise on a sled, or boat, probably the voice won't help, but in a car, which is where it will live most the time, it sure seems like the best piece of bread out there.