I got a Montana this past spring, overall it is great. However I got caught on my bike for about 5 min in a thunderstorm and the Montana stopped working, had water in the screen. when I contacted Garmin they told me that although it is water proof it should not be in the rain.
They covered it his time but said it was a one time deal. Quote from Garmin email response "If you continue to use this on your motorcycle please keep a baggie on your bike so if you get caught in rain you can put it over the device so you don't have to worry about the pelting of the rain causing water to get inside the device".
I think it is still one of the best GPS for dual sport, especially if you want to use it for other sports as well. I just think that the description on the website is a little misleading.