The format is quicktime, beyond that I don't know much about it aside from the fact that in general I despise quicktime (I would much, much, much prefer to see avi, mpeg, or best of all divx (though I imagine divx would require prohibitive amounts of cpu power on the camera's part, though 5-10 mb./min. for high res video would be awfully nice), but video was not the main reason I bought this camera of course).
That having been said, there's no facility to attach an external mike that I'm aware of, and I'm a bit wary of drilling holes in the camera (at least until the warranty expires :P ).
I changed the resolution to 320x240, and the problem was not as pronounced but it was certainly still noticeable. Other sites have said that this is only a problem at 640x480 30 fps but I can discern it in lower resolutions as well.