In the last couple of weeks I've tested the lens in different situations to learn more about its capabilities. Two main things that interest me are the effects of VR on shooting experience and image quality, and the minimum aperture beyond which diffraction becomes a problem.
As many already know, the proper use of VR is to half-press the shutter button, wait for the stabilization motor to engage (you can tell when it's working because it also stabilizes what you see in the viewfinder) and only then fully press the shutter button. Sometimes, when I want to take a picture of a very active subject (a bee for example) the VR gets in the way because the subject stays still for only a very short interval of time. If I cannot get it right there, it will move to another place and I have to change my position and/or re-frame. I found that the time it takes the VR motor to engage can make me lose the shot (well, because I need first to frame the shot, then half-press the shutter, etc.)... In such cases I turn the VR off and bump the ISO to get a good shutter speed. This way I can fully press the shutter from the beginning - the AF is fast enough.
Another interesting issue I wanted to clarify was whether the VR system has any negative effect on image quality - that is, if the shutter speed is fast enough to allow me to take the shot without VR, would enabling it degrade or improve the sharpness/contrast/color saturation in any way? I did an unscientific test to check it - I took a number of shots of a brick wall, handheld, at different apertures, with the VR on and, respectively, off. I only had time to test with the lens at 55 mm (I will try 200mm the next time), and I set ISO to 400 which gave me enough shutter speed for handheld shots even at f16. After comparing the images on my computer at 100% (f4, f5.6, f8, f11 and f16) I found out that there is no significant difference in IQ between the shots with VR on and the shots with VR off for the same exposure.
I also wanted to see at which aperture diffraction starts to become a problem. I noticed the fact that the photozone.de review of this lens did not show any results beyond f11, so I suspected that f16 might have some problems with diffraction. That is why I shot with apertures from f4 to f16 for the VR test - I planned to use the same images to analyse potential diffraction problems at f16. Again, after analyzing at 100%, I concluded that in both the shots with VR on and the ones with VR off, at f16 the images are noticeable softer than the ones at f11 and a bit brighter too (loss of contrast?). So it seems that there are signs of diffraction starting at f16... I did a bit of sharpening on the f16 imges and I was able to bring them closer to those taken at f11. Of course, these were all images taken at 55mm. I'll see what the 200mm test will bring.
Another thing I realized recently and used to my advantage is that at 55mm this lens goes to f4, while the kit lens stops at f5.6. I did use that extra stop (plus the VR) when shooting some low light photos recently...
Finally, this is not a macro lens, but with a little bit of cropping I can get the type of close-ups I'm interested in taking
Nikon D40, Nikkor 55-200mm VR @ 200mm
ISO 800, f5.6, 1/100 sec, center weighted average metering, VR on
Shot in NEF and processed with ACR4.1/PE5