I posted my first impressions about the recent Nikon D4 professional camera on the photography wiki: more details here:
http://www.techniphoto.com/wiki/index.php?title=D4_Nikon
The short version: the D4 is not a revolution compared to the previous D3 generation, more of an evolution: almost everything is better but the D4 is not a real game changer to photographers unlike the D3.
*higher resolution
*improved AF (yes it is possible !)
*improved UI/handling
*improved ISO performance (vs D3, less impressive vs D3s)
*much better video specification than other Nikon cameras (couldn't check this YET)
As a conclusion: probably the best DSLR as of today for reporters, events and action photographers.
This new flagship is not without flaws, however: this is not really Nikon's problem, but because of the Japanese government, they had to introduce a new battery/power system, meaning a new charger, new batteries and a seriously decreased battery life -> you need more (expensive) spares. Another thing is the new XQD card format: as of today, only Sony can provide them, and the D4 is the one and only device in the world using them. This is seriously increasing the cost of ownership (readers, cards) and I am not convinced at all by the added value. The buffer is big enough, and the extra speed is not a real need for "normal" shooter. The last CF cards were fast enough, as far as I am concerned.
Final conclusion: highly recommended to recommended depending on the usage.
