On Nikon's mini-site promoting the new D300s DSLR camera, there are samples that show a bit of the potential of using a camera that can capture both still and HD movie images (caution: heavy use of Flash here)
http://imaging.nikon.com/products/imaging/lineup/microsite/d300s/special/en/index.html#
Having the ability to capture video with the same gear you use for still photography reduces the load you have to carry, and simplifies the process of moving from still to movie mode.
http://imaging.nikon.com/products/imaging/lineup/microsite/d300s/special/en/index.html#
Having the ability to capture video with the same gear you use for still photography reduces the load you have to carry, and simplifies the process of moving from still to movie mode.