The D4 is going to be all about ISO, which is brilliant, trust me the ISO 102,400 native (note to the other poster, the D3S only does 12,800 natively, its 102,400 is extended) mode will make most photographers weep. The ISO quality on the D3S is amazing, it way less noice on 6400 than a D300 has on 1600. The same bump will happen on the D4 (ie. iso isn’t set in stone, there is difference in performance  at different levels between different cameras).

This camera will rock the socks off any photographer who doesn’t live in a studio or doesn’t have the luxury of setting up on location flashes for all their shoot, or doesn’t photograph stuff static enough to be able to use a tripod and low shutter speeds. There will be a D4X eventually for those people. The D4 will be the workhorse, for event, sport, wedding, press, etc etc. (and it will still be perfectly capable of delivering professional results in a studio, I seen more than one studio here in London that shoots on the D3′s quite successfully).

I don’t mean to sound harsh, but the MP addiction is ridiculous. I wonder how many photographs actually print in sizes larger than 10″ – 16″ @ 300dpi. If you consistently get this requested from your customers (as in, larger than magazine prints), you most likely have the budget to get a medium format (aka. Hasselblad) for this type of work. If you are a hobbyist, the idea of needing more than 12MP is even more ridiculous.

I switched to Nikon ages ago, because the brand i was on (I don’t want to name it and start a flame war), seemed to think that auto-focus point, viewfinder quality and most importantly ISO performance all was secondary as opposed to squeezing more pixels into the sensor. And I never looked back.