If you haven't been following Vincent Laforet's post about his 72 hours with the 5D mkII, he managed to make a short film using the 1080p HD feature before giving it back to Canon. After finally finding a place to host it (Canon came forward nonetheless) he's posted it here. My internet here sucks and it's still downloading, but at 1/4 size what has downloaded so far looks amazing. He shot it at night, between 5pm and 4am, so everything was done very low light using top notch fast primes. Read his initial review to get more of the story behind it.