I just mounted an older Garmin Nuvi (not waterproof) in a RAM Aqua box (it is waterproof) on my bike in preparation for a long distance ride. I was pretty impressed with the Aqua box before it was actually on the bike; the touch screen worked well through the Aqua box's screen and it really does appear waterproof. Even the wiring through the labyrinth in the back looked like a great idea and again, waterproof. But then I mounted it to the right handlebar and things went downhill. The Aqua box is too wide for the bike; I have the choice of blocking some of the instrument panel or some of the right mirror. Even worse is the visibility of the GPS screen, which in direct sunlight is about zero. The screen itself isn't bright enough (Nuvis are not meant for direct viewing in the sun) and the Aqua box screen makes it substantially worse.
I had thought the Aqua box might allow a lot of people to use non- motorcycle electronics on a bike relatively safely, and while it will do that it is a little clunky and hard to see the screen. In my opinion, this is not a good way to compete with a true, waterproof, motorcycle GPS. It does work though and for under $200, you can have a fully functioning, albeit somewhat hard to see, GPS mounted on a motorcycle. It might be great for the occasional user who doesn't even want to wire the GPS to the bike and only use it occasionally under battery power.
Brian