I understand the importance of high ISO, but when I look at my important images I rarely go above ISO 1600. The much bigger factor for me is dynamic range and color at lower ISO levels. The D800 and D600 really excel at low ISO levels where I shoot most often.
I'm not sure I'd make a change to Nikon over $800-900, but I am excited about the series of cameras Nikon has delivered for the past few generations. They have consistently provided significant technological advances. And in general, the cameras are very intuitive and ergonomically fit well.
Both companies have hits and misses with the lenses. If you are choosing pro level lenses, both companies have winners. The Nikon lenses generally rate well in comparisons but both are very good.
One area you may not have reviewed is the Nikon TTL flash system. The flash system is excellent and lets Nikon users automate flash in many situations through through the lens metering and flash control. The D800/D600 have an on board flash which is very useful in controlling additional off camera flashes.