There has been a lot of controversy lately about the brand new Nikon Nikkor 70-200 f/2.8 VR II lens. Some folks claimed the lens is utterly unusable for wedding photography because of the changes to EFL (effective focal length) compared to the older VR I lens. As usual with expensive gadgets, the noise to fact ratio skyrocked in the ensuing (sometimes emotional) discussion in several photography related forums. Interestingly, the EFL issue went unnoticed in all the raving pre-release reviews of the new VR II lens.
I just want to point to a thread on dpreview.com which IMHO is the most accurate comparison between the VR I and VR II lens to date:
The first three posts from user em_dee_aitch sum it up very nicely.