The TNVC GoPro adapter is good for filming "personal use" hunting footage in my opinion. It isn't production quality however. I say that because you get a large black ring around the video frame with the GoPro adaptor as there's no zoom capability with a GoPro. Even when a target is very close, it's difficult to even tell what it is when replaying the video. The design behind the GoPro adapter was so MIL/LE personnel can record their Close Quarters Combat operations. It works exceptional in that regard. It's just not as great for hunting type videos for production use. It's also difficult to capture what you see through the eye piece with any set-up. This is something I've been working on diligently for several months now. Testing DVR's, camera set-ups, frame rates, etc. The best results I've had for filming in the dark thus far have been filming through a TNVC PVS-14 Gen III using a Sony HD camera mounted to a tripod. The footage is very good. Make sure you're watching these videos in 1080p HD format.
The following footage is filmed with the thermal set-up that has given me the best results so far. Again a Sony HD camera mounted behind a thermal unit on a tripod.
Obviously I can't use either of these set-ups to film on a gun however. I'm testing a new DVR next week so I'll be sure to report my findings here when I do...