Apple PR:

Apple today announced that it sold (or delivered in the case of maintenance agreements) over two million copies of Mac OS X Leopard since its release on Friday, far outpacing the first-weekend sales of Mac OS X Tiger, which was previously the most successful OS release in Apple’s history. Sales included copies sold at Apple’s retail stores, Apple Authorized Resellers, the online Apple Store, under maintenance agreements and bundled with new Mac computers.

I'm surprised they don't count copies downloaded via Bit Torrent in that total; they've pretty much counted everything else. Still, good numbers, and probably about 40-50 percent of what the overall retail sales will look like for the life of the system.