Apple's standard operating procedure is to make upgrading from one version of Mac OS X to the next as bullet-proof as possible. Unfortunately, "upgrading" means buying a whole new copy of Mac OS X - which, in recent versions, has run $129 for a single version and $199 for a five-user Family Pack. Theres no separate upgrade qua upgrade.

This may sound a bit steep, but compare it to the upgrade prices for Microsoft's new operating system, Windows Vista, which has a four-tiered upgrade scheme: The Home Basic edition upgrade goes for $99.99, Home Premium for $159.95, Business for $199.95, and Ultimate for a cool $259.95.

Mac OS X Leopard will come in two versions, the standard version (which we assume will be offered for $129 - but we can't guarantee that since we have no special insight into The Mind of Steve) and Leopard Server, which - if it's priced like Tiger Server - will run for $499 for a 10-client set-up and $999 for an unlimited-client set-up.