Hi guys,
I was using the internal mic, which was picking up the IS sound a bit. Even with an external mic, you need to keep it a few feet away from the lens. I had gotten all the photos opps I thought I would get, and he kept singing away, so I figured I should get some video. That said, I could see myself kicking myself for shots lost sometimes!
Video size varies a bit depending on the scene, but is typically about 3GB for every 10 minutes in raw format.