How it works: Spotlight was another Tiger innovation that just never quite lived up to its billing. It was hobbled by slowdowns and some bad design decisions on Apple's part regarding what sort of searches you could run. While it's a bit too early to say if it's substantially faster at least Leopard Spotlight goes part of the way towards improving things by allowing you to run Boolean searches with the AND, OR, and NOT operators as well as narrow your search results in various ways. In addition, like Google, Spotlight now knows how to add and define words, so you can run simple arithmetical calculations (e.g. "7+5") or look up words in the dictionary, just by typing them into the Spotlight search box. Spotlight can now also search other Macs on the same local network as well.
Who will use it: Everyone who needs to find things on their Mac(s).