DSLR News Shooter has had the opportunity to play with the 1DMrkIV and wrote a hands on review of it. Interesting points: they confirmed it can record at all the 7D frame rate plus 25p. Some people are going to be happy! I would have expected a higher frame rate, just to keep in line with the 1D expectation of high frame rate in the still world.
With some luck, I should be able to put my hands on a 1DMrkIV next week and will try to post some sample clips (if the card slot is not locked!). The thing I am the most interested in testing is the HDMI output, so stay tuned!