As a counterpoint to the crushing disappointment that was Vista, which emerged with only a fraction of its promise intact, Apple’s OS X Leopard (10.5) is everything that Steve Jobs said it would become when Apple first placed that first unsteady cub in developers’ hands. Leopard is also a thick catalog of inventions and improvements that Steve flat neglected to mention — so thick that Apple had to resort to running the equivalent of a software project change log on its site for marketing purposes. You can’t chew through that list. I’ve had months to do it, and I’ll hit high points. The ones I choose, not those highlighted by Apple. I’ll be on Leopard constantly through the weekend and next week, so while I may be forced to speak to the familiar here and the Mac-curious there, I’ll make sure that everyone gets what they need to make informed decisions.What impresses me most about Leopard is that for its 300 changes since Tiger (OS X 10.4), the line item reading of which provokes a range of reactions from the head nod to the ear-to-ear grin, there is not one ounce of fat, no feature in Leopard that you’d opt to leave on the DVD the next time you install it. Instead, for all that’s been added, Leopard remains trim enough to run on a PowerBook G4 with 512MB of RAM. The very same OS is a robust, Open Group certified 64-bit Unix when run on Intel Core 2 Duo and PowerPC G5 machines with no need to buy a special edition. One of Apple’s marketing lines says that everyone gets the ultimate edition of Leopard because that’s the only edition there is. I’d argue that if Microsoft’s Vista product tagging is the basis for comparison, then all Leopard buyers get the 64-bit enterprise edition.One concern that you can cross off your list is stability. I’ve spent several months working with Leopard as a developer and administrator. I began rolling it into production, against Apple’s advice but not requiring its consent, at a point prior to its release when I judged it stable enough. I’d be pressing against the bounds of the non-disclosure to tell you when I felt Leopard hit its stride. Instead, I’ll just say that there is no need to obey the standing advice to wait for the first boatload of fixes before buying in. That’s true of Windows, and true of Linux, but not Leopard. Existing Mac users thinking of taking the leap can safely take ease of upgrades and installation for granted after they burn their most critical data to DVD or an external hard drive. Migration Assistant, which you can invoke at install time or at your whim later, transfers your user data and applications from Tiger to Leopard after what amounts to a clean install. The Leopard installer will let you do an overlay install, which updates the system software and tries to leave everything else alone. It is impossible to automate all possible cases, but I can’t imagine any user who could make Migration Assistant fail. Do be patient, though. Take measures to ensure that Migration Assistant runs uninterrupted, and understand that Migration Assistant’s estimated time to completion is a wild guess. In my experience, it finishes sooner than expected.Leopard drives as smoothly as Mac users expect, but for the first time in several years, Apple has used Leopard to challenge users to change the way they work. With so little time to button this initial story up and file it, I can only point to what I found to be the most substantial user interface enhancement: Spaces. This gives you multiple desktops, and you can switch among them via the keyboard, dock, or menu bar icon. It isn’t fast user switching, but more lightweight. The unexpected killer here is that Spaces lets you target specific applications to selected desktops. So, for example, you can arrange things so that Mail always opens in Spaces’ second desktop.You’ll find one Apple exec’s selected Leopard high points in this interview, and my thoughts on Leopard from a technologist’s perspective in my Leopard: A Beautiful Upgrade column. In the meantime, stay with me through the weekend and into next week as I keep building on Leopard coverage. As I said, you’ll get it all, and I promise that you’ll find a good deal here that won’t be revealed anywhere else. Software Development