Thank you so much for a wonderfully informative post. I love natural light photography and it sounds like the D4 will pair up nicely with my (legendary) 85 mm f/1.4 and also my 105 mm VR f/2.8. Both better low light performance, and better performance tracking moving subjects, are things I would really like to have, as well as the greater FPS and the large buffer for repeated shots. I don't think I'll mind the extra size and weight - I use my D300 with the MB-D10, and it's possible that the extra size and weight of the D4 will have diminishing marginal significance. I'm leaning toward it.