I suppose they had to make a D3s killer (something the 1D Mark IV is not). Kind of unfortunate this didn't come out a year and a half ago, however.
I love the promise of the new high ISO sensor and AF improvements, but I was sorely hoping for a different form factor: a modular, EOS-1V type design having 5-6fps naked and 10-12fps with a grip. That would have really shaken up the 1-series line.
My best guess is that this camera will be north of $6K, which will make it a difficult purchase to justify from a value standpoint, at least for me.