I used a Canon 1D Mark IV to shoot a Canon 5D Mark II with the new firmware shooting a video I shot with a Canon Rebel T2i. Check out my evaluation in my PhotoBlog...

Chad Soriano PhotoBlog (http://www.chadsorianophotoblog.com/)

Canon EOS 5D Mark II Video Audio Test on Vimeo

The background hissing is still terrible in that clip and most of the sounds are not clean.

I'm happy about the AV, TV, M and 25P options though... :)