Briefly: Snow Leopard Finder icons support QuickLook
One person familiar with the pre-release software notes that hovering the mouse pointer over an audio file in Snow Leopard's Finder will trigger a triangular 'play' button to appear on the icon itself.
Clicking the button will allow the audio file to play within the Finder, but without opening a specialized preview window. The audio file will continue to play uninterrupted even if the user brings an application to the forefront, but will halt when another file or window selection is made from within the Finder.
As the audio file is playing, a ring will form around the play button and slowly fill to indicate the length of the track that remains. A similar technique works for video files, displaying the video within the icon itself.
For both audio and video files, Snow Leopard testers users can currently press the spacebar to alternate between the icon preview and the traditional Quick Look view as it exists in 10.5 Leopard without any playback hiccups.
For other files, such as Pages, Keynote and Number documents (and their Microsoft equivalents), similar buttons appear on Snow Leopard icons to let users flick between pages or slides in icon view.
The latter features don't appear to be much use, people familiar with the software say, unless the user has their Finder's icon size cranked all the way up.
Separately, it's reported that another change in Snow Leopard will require users to enter their administrative password twice as part of any software install process: once when the installer application launches, and again right before the actual install process begins.