Reading some posts, it appears that the Optical Image Stabilization can cause some stuttering under certain conditions (I think one was panning). Are there times when turning off the OIS would improve the video quality or prevent stuttering? Would like to know what the pros think here. I had always thought that having it on was the best thing, but I really don't know.

I always turn it off when I have the camera on a tripod. Any movements will be deliberate and smooth anyway. The phenomenon that you describe is the OIS trying to compensate for the movement (panning or tiling.) The lens elements that move can only move so far, and the image stutters when the lens moves as far as it can. Rule of thumb: OIS isn't necessary on a tripod.