While I like the idea of a 70-200 f/4, and I only have the 70-300 D ED lens as a telephoto zoom, I think I will continue to save my pennies for the 70-200 f/2.8. Why? So that I can still have a manageable viewfinder and possible AF when auto focusing with my cameras (D700, F100, N70).
Now then, if I had a D600 and its ability to AF with a lens/TC combo with f/8, then yeah, I think I would get the 70-200 f/4.
Of course, the option to get the 70-200 f/4 + 300mm f/4 and a 1.4 or 1.7TC might be worthwhile, too. Haven't given it too much thought, though, still saving pennies for the SB-910 (next month!) and I have other hobbies that have been getting my attention lately (which really is another post - off to the CAFE!)