Nearly every Mac web site has posted some kind of Panther (X.3) review, and nearly all reviewers have missed the boat. The most revolutionary feature of Panther has been almost universally overlooked.

It is easy to find stories that hype or deride the new brushed metal look of the Finder. Most even mention how to "turn the look off," but none of them tell you why the metal is there and what the metal means.

In the days of OS 9, the Finder was built with a rigid series of implicit rules. These rules (covered extensively in John Siracusais "Spatial Finder" article on Ars Technica) were so sensible and reliable that most of us didnit even think about them- we just assumed that was how the Finder should work.

In OS X, the Finder was crossed with a NeXT-style file browser. The default behavior of windows and icons changed (many times in subtle ways). These changes caused some cognitive dissonance for those migrating to the new system.

In OS 9, windows were persistent. You could change a windowis size, position, and icon arrangement at will. This arrangement persisted until you, the user, changed it again. Months and years could go by, and these values wouldnit change. The Finder stayed the way you defined it.

In OS X, the shape, position, and state of windows changed randomly, depending on certain actions you took in the Finder- even those which werenit intended to cause a change in the windowis state. This caused some confusion.

In OS 9, clicking on an icon opened a window. If you clicked on that same icon again (or an alias) that window moved to the front. The Finder didnit duplicate that window. You could only have one "copy" of a given window open at any one time.

In OS X, the Finder could, and did, spawn multiple copies of the same window. Clicking on the icon would open a new view of the folder, which sat beside another, possibly different view of the same folder. This also caused some difficulties, not the least of which was undermining the metaphor of the Finder.

The debate has raged since, with many defending the pseudo "file browser" behavior of the OS X Finder, and many attacking its flaws.

With Panther, Apple has allowed us to have our cake and eat it to, and Brushed Metal was the solution.

In Panther, windows can have one of two states- Metal or Aqua. This is not just a matter of looks. Which look a window has gives the user important feedback as to which behaviors he can expect from the Finder.

Apple has designed File Browser functionality into the Finder. This File Browser, denoted by the brushed metal interface, has a toolbar, the sidebar, and "in-window" browsing (unless you opt differently in the Finder preferences). This mode, "browser" mode, behaves in a consistent way you would expect from the OS X experience.

The other mode of the finder, denoted by the "Aqua" appearance is a "spatial" (or Classic Mac OS) mode. When Finder windows are Aqua, they behave (in almost every way) just like windows did under OS 9.

Multiple copies of the same window do not open when you click on an icon- the window moves to the front. The state of the windows are preserved. Clicking on an icon always opens a new window even if you have this preference turned off!

In other words, Apple has created a fused Finder, one that has a built in File Browser that obeys the interface conventions expected of such a Browser, and a built in "spatial" (Classic Mac OS) Finder that obeys the conventions expected of such a Finder.

The user has clear visual feedback as to which behavior he can expect (Aqua vs. Brushed Metal) and the same window can be toggled back and forth between the two states, just by clicking the long "pill" widget in the upper right hand corner of a Finder window.

This is a truly revolutionary step. It gives us the best of both words. It is the secret behind Panther, and the reason behind the Brushed Metal.

Brushed metal is used in the iApps (iTunes, Safari, iPhoto, etc.). It denotes a "consumer" app. In the case of Panther, it represents a full-featured, integrated File Browser which can be turned on and off at will.

Now, users can browse spatially or use the Browser. The fusion between the two, and the ease in switching between them, has revolutionized the Mac OS.

To be perfectly honest, the integration and differentiation isnit perfect. The Aqua style windows lack the information the Mac OS 9 Finder used to provide- disk size/capacity used, the state of "snap-to-grid" and so forth. Apple should add these features back ASAP.

Also, the column view can be accessed in the Aqua windows, and that view undermines the spatial metaphor. The column view is appropriate for the Browser Finder, but not the Spatial Finder.

Minor quibbles aside, the new Finder is a work of art. As stubborn as Apple has been vis-à-vis the makeover from Platinum to Aqua, the fact that they have rehabilitated the Finder with its "old" behavior came as a shock- which is probably why most reviewers missed the significance (or existence) of the Aqua/Metal mode change.