The conversation about Snow Leopard's compatibility with older hardware has been dominated by complaints that it won't support PowerPC—something we've all known for months. But Snow Leopard will have some mixed implications for more recent hardware, too.
First, we have a possible bonus feature for last-gen MacBook users. According to Snow Leopard's "Enhancements and Refinements" page:
All Mac notebooks with Multi-Touch trackpads now support three- and four-finger gestures.
This seems to mean that older MacBooks, which only supported two-finger scrolling, will be brought up to speed with the latest in awkward finger-swiping technology. It sounds strange that Apple would leave capabilities like this unlocked for so long, but as hackers discovered months ago, that's pretty much what they did.
This is followed, unfortunately, by a swift kick in the penis: None of Snow Leopard's fancy new GPU offloading features, including h.264 video acceleration, will work on the millions and millions of Macs with Intel integrated graphics. Even worse? While OpenCL at least supports the Nvidia graphics hardware in last-gen MacBook Pros and iMacs, h.264 video acceleration will only work with Macs that have Nvidia's 9400m graphics processor, i.e. Unibody MacBooks. GPGPU and video acceleration features are closely tied to hardware, so this isn't necessarily shocking, just a bit disappointing. [Macrumors—Thanks, Max!]