I just used my iPhone with the Garmin app for 2500 miles of NY state backroads. For navigation, it worked fine, but the major downer is not being able to work routes on laptop then upload to GPS. Until a real solution to that comes up, this will never be a real solution imho. It could be right around the corner with Google maps. Dunno. It'd be really cool to be able to route in google maps, save to "my places", then just open a google app and there they are with turn by turn. Of course, they'd need to be available offline.
I used the RAM X-GRIP
. This is a pretty impressive mount. The phone didn't budge and its very easy to use.
For me, this isn't a long term solution regardless of future apps. I like the idea of redundancy, and relying solely on one unit is not a solution, although it sure was easy and worked well. My GPS quit charging 2 days before leaving on my trip, so I was left scrambling for a nav solution.
As for long term vibration, I can't say this is an option. I will say though that the X-grip is rubber mounted, and the phone didn't vibrate at all. That link has a video showing the phone getting shook as the manufacturers proof, but who knows in real world situations. I plan on using it until I decide what my next GPS will be. It's cool to have these options at our fingertips!