>This truly is a marketing gimmick. There simply is no >substitute for fast aperture.
If you already have a lens fully open and the shutter speed is still slow because the scene is dim, VR can improve images significantly. I've seen it, especially with my 70-200 VRII. It is an easy test in your home office. Dim the lights and take 10 shots with VR on and 10 with VR off.
VR can also allow one to stop down a bit for added DOF (sharpness) and image quality. With my 70-200 VRII and TC 20 III attached, I see an improvement in composing as VR stabilizes the image. (I've read this can help AF but haven't observed this).