I picked one up a week ago and took it on a camping trip. Great purchase. The only issue I ran into was that the spot I chose for the sticky mount (on the inside of the windshield, a couple inches below the mirror mount) caught the reflection of my dash in a lot of the shots. It'd be better to mount it to the outside, but then I wouldn't be able to start/stop it from inside the car.
How are you guys mounting it to the exterior of your cars? Sticky mounts? Suction cup? The only version available at the store I bought mine from was the helmet one, which came with head and helmet straps and four sticky mounts (two curved, two flat). I feel comfortable using the sticky mounts on my windows, since I can always pry it off and use a razorblade and solvent to get the residue off, but I'm not brave (or stupid) enough to stick one to the car body. Can the suction cup mount really be trusted for exterior mounting on a car?
Also, as a side note, I was watching the show "Whale Wars" last night and was surprised to see that a lot of the footage seems to be filmed with GoPros. In several shots you can see a cameraman holding what looks like some sort of steadycam with a GoPro stuck on top, and several of the people have one stuck to their helmets.