It's a great camera, as long as you play to it's strengths. You need to put it close to the action, if you try to sit back and film with it like you might with a more typical video camera you just aren't going to get very good video. If it is the only camera you have to work with then use it with decoys and put it right out where you expect the bird to come. I set mine 4-5 feet from my DSD jake to get the bird as it comes in to challenge the decoy. If you have another primary camera to use from your location then you can either use the GoPro in the decoys or maybe capture another view such as looking at the shooter. As far as settings, mine is set to 1080 @ 60fps, field of view set to narrow. This gives me the option of slow motion footage, and the narrow setting buys me a couple extra feet that I can set the camera back out of the line of fire.
This video shows what the GoPro can do when you get it close.
http://www.youtube.com/watch?v=Q0RFZR6t1OwMy two camera setup, Canon HF G10 and Hero 3 Black.