Eric Glam: Barney,Since you can't say the truth, I'll say it for you:The D3S is still the ISO king.Even if you down-sample the D4's 16MP 12,800 ISO RAW photos to 12MP,(or up-sample the D3S's 12MP to 16MP - the D3S wins.As simple as that.In the end - Image Quality is what it's all about.D3S owners - keep your camera.
I completely agree, and I shoot Canon. I blogged about this issue days ago, as it can be clearly seen from DPReview's own D4 samples compared with D3s, the clear winner. I also noted there the comparisons at ISO25,600, with the D3s, though in expansion mode, still beat the D4. I highly recommend grabbing D3s while you still can, and use the difference to buy a killer lens. :)
I like how Canon is breaking away from "standard" sensor sizes with this 1.5" sensor, somewhere just under Sigma's 1.7x APS-C sensor size. Size matters :)
That said, I can see Canon moving into "medium-format" territory in a future flagship DSLR. They moved into Cinema with the C300, and we never would've guessed that happening, right?