Quite a tricky one and some excellent advice given above.
Tom is right about the ability of lesser scanners to extract the full glory of Velvia 50.
Here is something I did a while ago to evaluate Velvia 50 against the then new Velvia 100F and also Astia 100F. They were all scanned with a low tech Epson 'perfection' 1200 flatbed and so are not nearly as dynamic as the originals, but at least a level playing field. The films reacted very differently and each can have its place in your camera bag. If you want pink sunsets and dawns, Velvia 100F will not render them very well.
You will need to click on the "tried and emulsional" link at the bottom of the LH frame, sorry, I cannot link directly to this.
As for the now new Velvia 100, I did some comparison shoots and posted them in the technical gallery here I think (scanned with an Imacon, so better representation of colour).
Being less than enamoured with the results, since Velvia 50 is being discontinued, I am now looking at using Fuji NPS colour neg, which is giving good results, but seems more grainy.