Resolution Independence Support in Snow Leopard? - Mac Rumors: "The benefit of resolution independence would be the ability for the operating system to scale its user interface smoothly to accommodate higher resolution displays. At present, most displays are around 100 dots-per-inch (dpi), meaning 100 pixels for every inch of screen display. If Apple were to introduce an ultra-high resolution display, it could have a dpi of 200 or 300. The same image viewed on these higher resolution screens would appear 2x to 3x smaller. Simply scaling up bitmapped images to fit the display would result in blocky/jagged images. If instead, they are described as vectors, as Apple is proposing, larger displays could smoothly scale the user interface to the size of the display."
Some details from MacNN.com...
"More crucial may be a dramatic shrinking in the size needed for OS functions, possibly related to cutting out duplicate localization, and to the implementation of "resolution independence," which replaces bitmaps with vectors that can handle any desktop size. The Utilities folder is expected to fall from 468MB to 112, for example, while Mail will be cut from 287MB to 91."
Another place where size can be cut is by eliminating the PowerPC code in Leopard. Currently, OS X Leopard is a Universal Binary. This means it has code for both Intel and PowerPC Macs. There are apps out there that remove whichever part of the code you don't need, but they can never remove it from the core of the OS. From the look of things Snow Leopard (10.6) will not support PowerPC (G4/G5) macs and thus won't need all that extra baggage. By slimming things down by getting rid of bitmap images and going to MUCH smaller and totally scaleable interfaces and losing the PPC code apps are getting smaller and will thus be faster. They won't take as much RAM, they won't take as much CPU power and thus better battery life and faster computers. Everyone wins - expect for those with 2-year-old G5 machines...sorry guys.