Bumping this thread has reminded me that I should post our experiences.
We installed one on each of our F658's before setting out to travel teh back roads of New Zealand for a month at Christmas.
Rain, man we live in the sub tropics and I have never seen rain like that which we experienced on the west coast of the South Island. The Kiwi's called it a "rain bomb", we just called it bloody biblical.
The USB outlets were installed on the dash beside the rev counter, and I used a lead to run to my phone in the tank bag. Worked perfectly and with the closed cover over it not a drop of water got in.
Burnzy's USB adapter is definitely the ducks nuts.