Before we take these deep dives, however, here's a detailed list of the changes you can expect to see in Leopard. We start with what most users will notice first: the look.

Mac OS X trumps Vista

Earlier this year, when Windows Vista was released, Mac users couldn't resist pointing out that Microsoft's long-overdue OS appeared to borrow heavily from earlier versions of Mac OS X. Apple had the Aqua interface; Microsoft called its version Aero. Slick colors, faded transparency, glowing buttons -- they all made Vista look subtly familiar to Mac users. Apple, with Leopard, appears to have returned the favor, most clearly with changes to the menu bar, the Dock and the Finder window. In our view, Apple's efforts work better at guiding users through the operating system without resorting to the cartoonlike look of Vista.

In Tiger, the menu bar at the top of the screen was a glistening white. In Leopard, the glisten is gone and the white is now semitransparent. When screenshots of a prerelease version of the OS hit the Web last summer, this one change caused a hue and cry among some Mac aficionados, who complained that the translucent menu bar represented -- gasp! -- a step back for Apple's notorious focus on usability.

The darn thing, they said in countless online forums, was much too transparent. You couldn't read the words in the menu bar, especially if you had a dark background picture. Apple listened. The menu bar in the release version now offers only a hint of whatever background image is behind it.

Also updated are the blue Apple icon in the upper left-hand corner of the screen -- it's been around since the first version of Mac OS X -- and the blue Spotlight search icon in the upper right-hand part of the screen. Both are now a flat charcoal gray, adding to the sleek, more unified look of the Leopard menu bar.

Even more obvious are the changes to the Dock. Earlier incarnations showed icons floating above what looked like a strip of Scotch tape. The new Dock, when positioned at the bottom of the screen, looks as though the icons are sitting on a reflective glass shelf. (Application windows that are moved close to the Dock also reflect.) Gone is the small black triangle used to designate an active application, replaced in Leopard by a small, bluish LED-like glow.

In terms of function, the Dock offers a major improvement with what Apple calls "stacks." The goal here is to help users better organize their files and folders. Drop a folder onto the dock and when you click on it, icons representing all of the files inside the folder arc out across the screen.

If you have more than about 10 items in the folder, however, a translucent window pops out showing your files in a grid. Click on the file you need -- whether it's in one of the short, curved arcs or the translucent grid -- and the associated app launches.

Moving the cursor over a Dock folder and holding down the mouse button or trackpad clicker yields a contextual menu that allows users to organize files by Name, Date added, Date modified, Date created or Kind. There's one caveat, however, when it comes to stacks: If you place your dock on the right or left side of the screen, the way-cool arcing feature doesn't work -- all you get is the grid of icons.

For those who like their Dock positioned on the right or left side of the screen, Apple has offered up a late surprise in the final release of Leopard. Now, when the Dock is positioned vertically, it no longer looks like a glass shelf turned on its side; instead, it looks like an updated version of the two-dimensional Tiger Dock, sporting a translucent, dark background instead if the old Scotch tape ribbon. It's clean, elegant and modern. Good move, Apple!

In another break with the past, Apple has done away with the brushed-metal look that used to grace Safari, Finder windows and -- several versions back -- iTunes. It's been replaced with a unified gun-metal gray color with a subtle sheen. Although brushed aluminum may have had its fans, many users wondered why it was ever introduced, since it didn't carry over to all programs and led to a confusing user interface -- hardly a feather in the cap of a company that prides itself on avoiding such pitfalls. Icons throughout the OS have also gotten a touch-up; between that and the new, uniform coloring, Leopard goes a long way toward cleaning up the look of the OS.