The Mac OS X Spotlight menu (the blue circle in the upper right corner of the screen) is incredibly annoying. You decide to use Spotlight to find something, so you click the menu or press Command-Space, you type your search string, and then you remember how annoyingly slow Spotlight is. And you can’t decide to do anything else on the computer while you’re waiting, because clicking anywhere else will abandon the search.
The key to making Spotlight useful is to change Command-Space to pop up the Spotlight window instead of the Spotlight menu. The window can perform a search while you’re doing things in other windows – the menu can’t. So the frustrating slowness of Spotlight becomes tolerable because you’re not locked out of your Mac while waiting for the search results.
You can change the mapping by opening System Preferences. Click on Keyboard & Mouse. Then click the Keyboard Shortcuts tab. Scroll down a bit to the Spotlight section. Uncheck the checkbox next to “Show Spotlight search field”. Double-click the shortcut area at the right end of the line that says “Show Spotlight window” and then press Command-Space (or whatever you want to use). Now, pressing Command-Space will open the Spotlight window with the insertion point right in the search field, waiting for your input. While waiting for the results, you can work in other windows.