nearly a month after having aquired a D800 and used it extensively, I can say DXO is right. I don't know about the score part, but about the part that it is indeed the best sensor on any 35mm DSLR to date. Nothing, and I mean nothing I've used from canon even comes remotely close. DR is as stunningly high as they claim and high ISO performance is surprisingly good rivaling the 5DIII on printed output.
It will be interesting to see how canon will respond with the 5Dmk4 in 3 years. I suspect they are done with 20MP and the next 5D body will go back to the original 5DII formula that proved so successful: push image quality, not frame rate.