Spaces is convenient, a must for laptop owners. Spotlight is much faster, more thorough.
Spaces may be overlooked by unknowing users. Spotlight's options are quirky, lack configuration.
Spaces: a hidden time-saver?
Most users starting Mac OS X Leopard for the first time may not even know that Spaces is available; unlike Apple's practices with Spotlight or Time Machine, the icon for Spaces is missing from both the Dock and the menu bar by default - requiring the user to either drag the icon there by hand or by enabling an option in the associated System Preferences pane.
System Preferences pane
Once enabled, the interface is as smooth as could be hoped for and offers a surprising amount of control for what could easily have been a throwaway experience: instead of just letting virtual desktops sit as an abstract concept, Apple makes it easy to understand by using spatial reference points. On the most basic level, the software lets you switch to and open programs in different spaces just by holding down the Control key and another button: using one of the arrow keys will move to a space set up in that location, while using a number key jumps immediately to a preset space. Either command happens almost instantly (faster, in fact, than a screenshot can manage) and provides a helpful slide transition that makes it clear as to where in the Spaces grid you will be. Clicking on the Dock icon for an app in a different space will also jump directly to that space. Effectively, beginners never have to memorize which space they need; while power users do not have to deal with the beginner's interface if they dislike it.
Veterans have even more control than this. In addition to setting up as many as 16 different spaces -- a feature likely only to be used by the most dedicated professionals or server administrators -- users can also pre-assign programs to certain spaces, which saves the trouble of ever having to recreate the spaces every time a program is shut down.
The true star of Spaces, however, is its at-a-glance view. Like Expose, hitting the function key shortcut or clicking the Dock icon (when available) brings up a view of all relevant areas: in this case, every visible space. This not only provides a quick way of previewing a space before jumping into the new area; it lets you shuffle programs from space to space without a complex setup process. To say that this is helpful is a mild understatement: the full view takes virtually all the guesswork out of setting up an ideal virtual desktop layout.
If anything, the only real drawback of Spaces may be that many users will assume that they have no need for it. Admittedly, the feature is not especially useful for the most casual of users, who only ever run one or two programs at the same time; for users who regularly keep e-mail, instant messaging, and other programs open at once, however, Spaces makes it possible to task-switch without juggling windows. For those who use Apple's portables, this may be the difference between using the stock display and buying an external LCD. Spaces may not be the linchpin of a Leopard purchase, but it adds significantly to overall appeal in the right circumstances.
Spotlight is faster, better, stronger
Anyone who has used Spotlight in Tiger on a regular basis can attest to an equal mix of pleasure and frustration: most searches indeed found what users were looking for, but more complex searches were largely impossible; and no matter what the search, the results always lagged behind the user's typing, defeating those who would use Spotlight as an alternative to the Dock or Blacktree's Quicksilver for launching programs.
Quite simply, most of those complaints have been wiped out in one fell swoop by the Leopard version. Even after days of frequent use, Spotlight almost always brings results as quickly as one can type: the results are speedy enough that Apple has actually shortened the shortcut for launching a Spotlight to just the Return key. The search tool also finds many more item types than it has in the past, providing entries in the Dictionary program and other specific categories; it will even perform basic math without opening Calculator and handles standard Boolean tags, such as "and."
Standard Spotlight search with extra categories
Spotlight also puts far deeper hooks into the operating system than before and, at last, seems truly pervasive. In the Finder, Spotlight is no longer limited to just a basic name and location search; users can narrow searches down to specific formats or time-sensitive details. Users seeking help also no longer have to open a separate Help Viewer app just to find a specific command, since Spotlight is embedded in virtually every Help menu and will point to menu items as well as list any help topics.
Enhanced Spotlight search in the Finder
Spotlight in a Help menu
The upgrade will likely never completely replace Quicksilver or other alternatives, and includes a few nuisances that may deter experts. Leopard's version of Spotlight refuses to limit Finder searches to specific folders by default, always forcing the user to narrow the search after the fact. It also lacks any kind of significant programmability; users cannot set shortcuts or otherwise change behavior beyond prioritizing certain kinds of files over others. In my experience, however, these issues are small. The sheer speed and flexibility encourage much heavier use of Spotlight and finally live up to the expectations set in 2005 with Tiger.