Apple today announced that it has sold 2 million copies of OS X 10.5 since launching Leopard on Friday. Who knew there were 2 million Mac users out there? Just kidding. No, seriously.

That figure includes copies of the OS sold through retail stores, Apple's online store, and copies delivered as part of maintenance agreements.

The bigger question is if this is a sort of blockbuster release. Everyone who wants Leopard will have rushed out to buy it on opening weekend. And next week the sales will slump significantly. Our guess is that the first weekend sales don't necessarily predict the overall success of an operating system. Rather, they indicate the degree to which the public bought the hype surrounding an operating system.

Last year Microsoft said they expected 200 million computers would have Windows Vista installed by the end of 2007. As of this week, the company has sold just 88 million licenses, which is still higher than many people had predicted.