I've started recording my IFR lessons and mounted it to the side of my headset.
https://www.youtube.com/watch?v=gLyvySf2Zp8
I find this mounting location to be the best for personal reviews but it does pose a number of problems. First, a few people have commented that it makes them dizzy or make it hard to follow. Secondly, it's heavy. If you spin your head REALLY fast (faster than you would normally when flying) it will twist your headset. Could be a distraction if you're not conscious of that. It also can slightly get in the way a bit if you have a passenger and you both lean into the panel or something. I will say that these issues have been minor to non-existent for me but they do exist. The advantages of this mounting is it always looks in the direction you do. You can pan the camera without taking any hands off of the airplane. And it provides a good mount that goes with you between aircraft.
Other mounts I've seen work well are the 45 degree angle view forward from the passenger window using the suction mount. This gets the panel, you, the side, and one half of the forward view. Kinda like this view only a little more forward facing:
http://www.youtube.com/watch?v=58l6DVzQaKs
Oh, hey, that's the 152 I flew. It's a good video, guys gets all teary and everything.
Then there's the rear mounted option. This works well for the smaller 152s and some other aircraft I've seen.
http://www.youtube.com/watch?v=8Aw2Zs9xK2A For many planes though the forward seats or seatbelts (172P for example) get in the way.
What I would do is take the GoPro and start recording and place it in many different places in the plane. Then, take that video home and see which ones you like the best and figure out a mounting option for it.
As for distractions, only once did it ever distract me and that was in a 152 with a Y splitter into the audio jack that came loose and caused me to loose audio in my headset on takeoff. Quick change out and I had it ripped out and thrown away. I've since replaced that audio jack and also have decided to avoid utilizing the same audio jack (such as plugging the audio into an empty back passenger jack in the rear).
Other than it suddenly falling off or getting in the way like mine did with audio I don't see any distraction and it's definitely helped me already to review my flights and learn many times what I would normally learn from a flight. Set it, turn it on (don't forget that part), and then you can forget it's there. Plus you get a neat memento to show people on PoA!
Now you can show off those greaser landings.
P.S. Remember that the audio cable must have a way to reduce the dB coming from the panel. I had a few flights with no audio because I couldn't get my home-built resister cable to fix the audio properly.