I have used a camera (ContourHD and later a GoPro3white) for filming my aerobatic routines.
I see lots of things on film which I don't notice during the flight itself, because so much is happening. I'm getting way more from each tow when I use the camera.

From time to time the operating of the camera can be a distraction, in much the same way that other new gear can be. This is valid for both the mounting (suction cups failing) and operating the camera.
However, with proper preparation and the right mindset I believe you can operate them safely.