From Mac OS X 10.5 Leopard onwards, while the Spotlight menu and find-as-you-type list of results on the upper right corner of the desktop remained essentially unchanged, this neatly organised window disappeared, and the Show All option simply triggered a new Finder window with the search results amassed in an unorganised fashion. If you didn’t find what you were looking for in the first results Spotlight displayed from the Search menu on the top right, you’d have to perform more organised searches with various filters and criteria directly from a Finder window. But the overall approach was less clean and clear than under Mac OS X Tiger. On the other hand, Spotlight got better as an app launcher and new features were introduced, like the ability to do quick calculations from the Spotlight search field itself.
When the Spotlight interface was finally redesigned with the release of Mac OS X 10.10 Yosemite, it was great to see that Apple was revisiting that kind of search interface, with a panel front and centre, and with the results organised in categories in a similar way as it was under Tiger. Since I upgraded from Mac OS X 10.9 Mavericks to 10.11 El Capitan avoiding Yosemite completely, I only started using this new Spotlight interface in recent times. And I have mixed feelings about it.
This is a terrific analysis of the behavior and design choices of Spotlight for OS X Tiger and the latest El Capitan. I agree with Riccardo – the organization of results in the original interface still looks better.