For a lens that has IS...you might as well use it handheld. None of the wide angles have IS except for the 24-105L. Your hands will always have movement. Vincent Laforet used a gyro-type attachment to keep his handheld work steady.
A longer lens will need the IS in your hands do to the size. You will always move, it will never be like a tripod. Shooting video will in no way use the IS motor in any different way than a person. Many people have IS running for far longer than 12 minutes with only momentary breaks in between.
Ever shot race cars and panned all day long? Or sports games? At autocrosses ive had my IS running for a good hour nonstop with only maybe a second or two break between cars. I keep my focus on the * button so I have it running focusing and tracking even when im not firing my shutter so I can track til the cars are in position. This keeps IS running.
In actual use, I don't think IS will be any form of problem unless it is on while on a tripod. Then again, a some of the new lenses can sense that and turn IS off.
As for the microphone, im sure in use this won't be an issue. I'm sure the microphone has a frequency cancelling function to ensure wind and low hum is not captured. Many audio devices have this as well. Then again, audio for a video will need to come from a much better source if it is anything serious. Nice mics and a preamp are in a different league than this camera. However, for quick location sounds, etc... that can be mixed in, it might be fine. I would not really on this mic for the dialogue of a movie however. I'de feel better even just synchronizing to a time code by estimate. Basically I would watch the audio recording's time code prior to hitting video record and then make not when the video started rolling. Won't be precise, but in post, you should be able to line it up just fine. Its not that hard.
I have just been spilling over with ideas for this new camera. I wish I could have preordered 3 instead! The store tells me they should be calling in the next few weeks...I hope so!