CNET’s MacFixIt:

If you’ve taken a look at Apple’s sneak peek of its upcoming revision to OS X, you might wonder if your system will be able to run the operating system. In recent versions of OS X, some requirements have resulted in older hardware no longer working properly, including the drop of PowerPC support in Snow Leopard, and Lion not installing on some of the earliest Intel-based Mac systems.Unfortunately Apple has not yet officially released the system requirements for the new OS, but the developer release that is being issued to members of its Mac development community does contain a list of supported devices.