I've just posted a quick demo video here http://www.vimeo.com/2351776 for those interested in getting full aperture control while on video mode. Works the same way with Contax or Leica glass. Beware a few manual lenses will clip the mirror of the 5D and so cannot be used, most are fine though. This level of control is not possible at the moment with Canon EF lenses.
Dan
Dan