The Developer Preview should work on any Intel-based Mac, and has been tested on Mac OS X 10.6.8 and 10.7.0.
This is an important first step in the new world order for Java and Mac OS X. Java 7 will be the first Java release for the Mac not released by Apple. Once upon a time, the Mac was considered the best platform for Java. When Apple announced it would discontinue official support for Java, many began to question the future of Java on the Mac.
As a Java developer, I hope Oracle will continue to put out a quality product so that I can continue to make my living on my platform of choice.