Someone asked in a previous thread about Garmin vs Phone, and this was my take on the downsides of the phone, and what I liked about the Garmin;
(Downsides of a phone)
For me, battery life, finding a mount that seemed secure enough at a reasonable price, heat build up running the GPS & inability to have the screen on without contributing significantly to that heat build up , weatherproofing.
The Garmin 800 I use hasn't given me any trouble so far[1], loaded with OpenStreetmap mapping, and it leaves my phone to be a phone.
I think it may be the best bike thing I ever bought.
[1] I've ridden pre-planned routes (loaded from RidewithGPS), ad hoc routes using the mapping to follow bike routes and check that "wonder where that goes" roads don't end in dead ends, and let it navigate me back to where I was staying in France when I had to cut a circular ride short unexpectedly in an area I didn't know.
) provided that the wheel size is correctly calibrated. Calibrating the wheel size can be a bit difficult, since it involves riding your bike in a straight line for a fixed number of wheel rotations, then measuring the distance covered.
