This spec list comes from a Canon Camera tester.
* 1.3 crop
* Images ~16MP
* ISO 50-26500
* 8MP sRAW1 format providing images that seem to best 1D3 files in detail [typo corrected]
* Very clean images at ISO 3200. 6400/12800 take further processing very well
* Slightly faster FPS than 1D3 in real life shooting
* AF greatly improved and very good in low light (actual comment was ‘Nikon fast’ ;-)
* Liveview AF – not up to fast sports use, but very usable otherwise
* Video as with 5D2
* Screen as per 5D2
* Ergonomic improvements with grips – some buttons moved
* Feels faster and more responsive in nearly all aspects of real use.