Hi Frederich... you are quite correct regarding the speed of the lenses; this D7000 gives a lot more life to my older, slower lenses that are of reasonable quality. However, in my case, many of my shots are in low-light conditions, where the use of a flash is just not possible. Given the limitations of the D70 AND my glass, I never even attepted to get various shots, whereas now I have the camera technology.... just the quality (and fast) glass required.
One of my more odd (mentally confusing, that is) shots is a timed exposure of the bushveld with starlight the only ambient light (no moon!) available, at midnight and the landscape to the horizon is full of colour as though it is a sunny day (Shot 30sec, 50mm f1.4) and the stars are visible in a blue sky
My prime reason for tending towards the 70-200 f2.8 is to get full funcationality with a 2x converter, giving me a (reasonable?) reach in the bushveld of 400mm (plus the crop factor) while still having the ability to exploit VR and autofocus, both of which I believe I would lose on an f4 lens. I am astounded on the clarity of shots, even at ISO3200 but have not yet undertaken may tests beyond this. I am in no rush to collect new glass (my bank manager says NO!

) so maybe the f4 could suffice. Will just have to wait and dream.
I have learned over the years to never compromise on quality, an expensive lesson in my early days in photography, and will thus wait till the best can be placed in the bag.... or I will just have to make do with what is in there already.