This is one interesting camera. While Nikon has still got the lead with low noise image capture I think Canon is leading with features, and this has two big features:
The multi-resolution RAW format is a boon, no longer does each shot need to be 21 megapixels, you can select from 3 different resolutions, from 5.2, 10 and 21mp. As wedding photographers, you can drop the resolution for those "filler" images, which will cut down the drugery of handling 600 huge files.
And the real big question, high definition video, what will this mean? As an owner of the 5D Mk2, you will be weilding a video camera with a significant quality advantage over the average videographer, consider Canon's range of SLR lenses and a full chip sensor, you will be holding a great video tool.
Will this mean a further cross over for photographers?