Taking it one step further in the next version of Mac OS X, dubbed Snow Leopard, Apple is incorporating QuickLook into the file's icons themselves, making it even easier to preview your media without even having to open a program. When the user rolls the cursor over the desired file's icon, a gray triangle will appear. When clicked, the icon will show a full preview of its contents.

For other types of files such as Keynote presentations or Microsoft Word documents, QuickLook will allow you to flick through the pages and slides in the file without having to open up the respective application.
Yes, this will definitely be a nifty feature to have, but unless you've got your icons cranked up to the maximum size, it may pose as a bit of a challenge to preview your files in that tiny icon view.
Snow Leopard is the next generation of Mac OS X and is due sometime in 2009.
Credits to AppleInsider for the find.
