Quark has a helpful chart that compares features between QuarkXPress 6, 7 and 8 at their newly redesigned online store.
I found it fun to see a concise list of improvements added to versions 7 and 8. See it here.
Jay Nelson is the editorial director of PlanetQuark.com, and the editor and publisher of Design Tools Monthly. He’s also the author of the QuarkXPress 8 and QuarkXPress 7 training titles at Lynda.com, as well as the training videos Quark includes in the box with QuarkXPress 7 . In addition, Jay writes regularly for Macworld and Photoshop User magazines and speaks at industry events.