What it is: Last year, we were all impressed by a feature embedded within Time Machine that let you quickly preview the contents of most documents, without launching the programs that created them. That feature - dubbed Quick Look - is now pervasive in Leopard, especially in the Finder.
What's new: Basically an enhanced preview, Quick Look lets you instantly access a live preview of a file without having to open an application. For example, you can view a large, readable preview of a PDF file and flip through that file's pages, right in the Finder.
In the case of a movie or audio file, you can watch the video or listen to the audio with one click. And if the default preview is still too small, another click lets you preview the file at full-screen size.
Quick Look supports many common file types - including text, images, movies, PDFs and Word and Excel documents - out of the box; developers can supply plugins that add Quick Look support for their own documents.
This feature should be especially useful for previewing photos and movie files, but it will also come in handy whenever you want to take - well - a quick look at a file without launching another app. DAN FRAKES