The filter came in today. I took a few quick ones with the digital for instant results. The results are quite nice-better than I expected. Since Velvia 100 is a little to the magenta side, a typical warm up filter can put it over the top with magenta. So this CC10Y may be a better option. When I shoot a roll of Velvia, I'll do a comparison with and without it. Here are the results with the Nikon D300 and "flash" white balance a few minutes after sunset.
no cc10y filter.jpg