The following stats are taken from the Nielson Videoscan ratings information in Home Media Magazine:
Data up to and including the week ending March 18th 2007:
Based on comparisons of week to week sales ratios from the same source, we can estimate that for the week ending on March 18th 2007, the sales for Blu-Ray vs. HD DVD were roughly 100:23 respectively, or just shy of 4.5:1, which is also about the same as last week.
All information was collected by Merlin at HighDefDigest here:
*Check the link for some pretty pictures of how the numbers look on graphs on a week to week basis.