I went for the D800 knowing the D810 was immanent and having a good idea of the specs (Nikon rumors had some confidence and I also spoke to someone from Dreview who was under NDA but confirmed some things).
I had some events to shoot, wanted to capture my new baby in the best way, and knew the D810 would be much more than the D800 (in total I saved close to $1000 over D810).
The D810 gains around half a stop at the new lower base ISO 64 which is what was expected as Nikon increased the deep well capacity. This doesn't affect DR any where else of course. It looks Like Nikon did do some tweaks in how the high ISOs are handled, this may decrease some noise but there isn't;t much data yet. DXOmark's ISO score is actually a combination of noise, DR and colour depth. Basically it is the highest ISO that can give an "acceptable" image where acceptable is defined as a minimum noise, DR (8 stops) and colour depth.
This has pros and cons. The noise might be very low at a high ISO because a sensor has done a load of filtering but this will reduce the DR because blacks turn gray and whites turn gray as the noise is smoothed out. So it is nice to not only measure the amount of noise in the image but check the image is still usable. However, at some high ISo settings the DR or color depth may not quite be high enough to be counted as "acceptable" by their definition but the noise may be significantly less than another camera. So the D810 might have slightly be very high ISO characteristics but the DR gets too low at the d=same ISO, which is entirely expected.
I wont bother swapping to a D810, I would loose close to $1000 for marginal changes. Will put that money towards glass, or simply set it aside to buy the D900 in a few years which will come with a whole new sensor.
