I can personally attest to how popular the mouse is. I ordered one from Apple's online store two weeks before Christmas. The ship time showed 2-3 days. This never changed until just a few days before Christmas when Apple changed the shipping time to "On or after January 4th". Runs to three Apple Stores and four Best Buys didn't do me any better – all were sold out of the Magic Mouse.
The NPD sales data included only standalone sales of the $69 Magic Mouse. "The figures did not include the bundled Magic Mouse that comes with each 21.5-inch and 27-inch iMac.
For those keeping track, here are the top five mouse vendors in the US for November 2009: