Now that Apple has blessed its users with a release date for the next version of Mac OS X -- it's the 26th, in case you didn't hear -- the next order of business for anyone planning to upgrade is to step back, take a breath, put down the credit card and think things through a little.

Is a move to Leopard smart? Your call, obviously. But assuming you give Apple a nod and your US$129, here are the questions to ponder as you prep for the Friday after next. We'll start with the basics first.

What is Leopard? Leopard (Panthera pardus) is both the name of a big cat and the code name for Mac OS X 10.5, the latest in a string of operating system releases from Apple that go by names from the family Felidae. The current operating system, Version 10.4, is Tiger, which was preceded by Panther, Jaguar, Puma and Cheetah, in reverse order. It is the first major release -- in Apple's eyes, that means a shift in numerical nomenclature of one-tenth of a point -- since April 2005. It also marks the longest time between releases since Apple started rolling out Mac OS X.

As to why Apple CEO Steve Jobs and company insist on naming their operating systems after cats, you'd have to ask them. But with 41 species altogether in the family, there are enough to keep going for another 43 years or so.

Mac OS X "Chinese Mountain Cat," anyone?

Why would I want to spend US$129 on a new operating system? Tiger is working fine. We're betting you're taking a subtle shot at Windows Vista here. If not, Apple says it has more than 300 reasons for upgrading, citing the number of new features it claims that Leopard has. Many are under the hood and hard to spot for all but the most dedicated -- as in the Apple Dictionary, which the company says now includes "a dictionary of Apple terms." Feature or market-speak -- you decide. But there are several that make most everyone's justification list, including these five: Time Machine, Boot Camp, Parental Controls, a revamped Desktop and a more powerful Spotlight seach.

Whether the changes are worth the US$129 -- US$109 at Amazon.com after rebate or US$116 with the educator/student discount -- is, of course, between you and your bank account.

Will my Mac run Leopard? Apple has struck some older PowerPC-based Macintoshes from the upgrade list by requiring at least a PowerPC G4 processor running at 867 MHz. That means the 800-MHz PowerBook G4, 800-MHz iMac G4, 800-MHz iBook G4 and others of their ilk and age are out of luck, officially anyway. All Intel-based Macs are Leopard-ready, however, as are all PowerPC G5 systems.

Leopard's other requirements are 512MB of RAM, 9GB of free space on the hard drive, and a DVD drive.

I've got three Macs at home. Is Apple selling Leopard in a Family Pack? Yes. Apple is already taking preorders for a five-license edition, priced at $199 list. Leopard's Family Pack license sports the same conditions as Tiger's, which means you can install the operating system on up to five Macs in the same household (machines with kids at college count). The Pack is an unbeatable deal: US$40 per machine if you have five Macs, US$50 each for four, US$66 apiece for three.

What should I do before I upgrade? Back up. Accidents do happen, even on the Mac, and if an upgrade sours, you'll wish you had played it safe. At the least, you'll want to back up data files -- your iTunes library, documents, photos and the like -- to an external drive, flash drive, CD or DVD. A full backup is even better, and a bootable backup is best. SuperDuper, a free backup program, lets you clone the boot volume of your Mac so that if the Leopard upgrade craps out the Mac, you can boot Tiger from an external drive. Just make sure your backup hard drive is large enough to hold all your files. You know how fast all those vacation pictures can add up.