I use a gun mounted GoPro2 (custom built), a GoPro2 mounted to the dog with some screws and wood glue (j/k http://thesugarcoat.com/UniversalCamCollar.aspx
) and I just got my GoPro3 Black which I plan to wear with a head mount.
The GoPro 3 Black is $$$, but is AWESOME. You can shoot high res video in 48 fps and still get great performance in low light. The gopro 2 also has short recording and battery times (about an hour or so), so you needed extra cards and batteries. The new Black edition has a built in remote to turn on filming which saves battery and space. YO\ou can turn on all wifi cameras at one time, so this feature is great for multiple shots. The black is also crazy small, which is important to consider if you are mounting on gun for both added weight and the shock on the camera due to mass.
They will also survive anything. I was hunting with my pro last year and while shooting ducks on the ocean, my first attempt at a mount exploded due to the recoil. The camera (which had the foam float) fell overboard. While trying to retrieve it in heavy current, I ran over the camera and it went though the prop wash (but wasnt actually hit with the prop). I got the camera back, and was using it the next hunt. Since the camera was running I got everything on tape, including the bird dropping as the camera hit the water, shots of the ocean floor, and harrowing flurry of prop wash.
I would love if another company could compete with GoPro and bring the prices down further, but for the time being, there is no other option, as even the GoPro2 Hero is still far beyond what other companies offer.