In terms of video and audio the new 5D has a few significant improvements.
> The new Digic5+ image processor should increase low light sensitivity, add higher ISO levels, and reduce chromatic aberration.
> There is a headphone out for audio monitoring and manual audio record levels.
> The ability to record I-frame or IPB is a great option. I'd like to see the I-frame video.
> The HDR addition will also get plenty of use in the timelapse video world.
> 4G automatic file partitioning allows you to record continuously for 29min 59sec.
> Records to CF or SD cards.
Still no word on whether there is a clean HD out. So, is it worth the $3500 price tag?? You be the judge.
(UPDATE) PlanetMitch from Planet5D did a hands on review. Check it out.