...."Not too impressed with several of the comments about the D5. If I need to step up I would only go to a D4S, if that."...
I have a D5 since last March; before I had a D4s to my entire satisfaction. I must say that the negative comments with regard to low dynamics at low ISO puzzled me. I decided to make a serie of landscape pictures at ISO 100 and high dynamics (alpine pictures with snow etc), which convinced me that it was a non issue in real life, at least with the sort of pictures I'm taking. The main purpose being action / sports photography: I can say the AF of the D5 is better than the one of the already perfect D4s; high ISO > 10'000 is not forbidden territory anymore.
Conclusion: yes the D5 is another major improvement; but the D4s is still a perfect camera; the only reason I changed, was to have "the latest one"
Landscape with a D5 & 300mm f/2.8 VRII
D5 & 28-300mm f/3.5-5.6 @ 85mm f/8
and two pictures in the D5's field of expertise: sports / marathon:
D5 & 300mm f/2.8 VRII