So, like Brain I have 3 GPS capable devices, unlike Brian, one of those is my govt. tracking device, AKA "Smart phone". On my last trip to CO I was using my Garmin Montana, unknown to me was the fact that the mapset loaded was NOT routable and I needed to get back to my daughters house and I had no clue as to how to tget there... My second GPS is my Garmin ETrex30, not user friendly for eyes that need cheaters to read. Last, but not least, the cell phone. Got me back. The issue? Not glove friendly and no dedicated mount to keep it within eyeball reach. Otterbox and Ram do make a weather resistant case, which I will be ordering soon and I know quite a few who use this with success, but generally speaking it is too stream music to their helmet and/or to monitor incoming calls, helpfull for the busy buisness guy (who is smart enough to pull over for the conversation).
So, my choices? Zumo 550, bluetooth, MP3 player, and XM capable for the long trips. On the ADV bike I have the Garmin Montana 600, it has multi layers so I can have the street maps overlayed with Topos overlayed with satelite imagery from the Birdseye supscription. The Etrex is soley as backup, small, Glonass and WAAS reception so it is far more acurate and much more likely to keep a signal when in wooded areas, which is especially nice on the dirtbike when I'm checking out new to me trails.