I know nothing about QuarkXpress or InDesign as I haven't ever even started up either application. I don't know anything about Photoshop either (shocking, no? I don't mean my ignorance, since I am sure you have all grown accustomed to that, rather I am speaking of the fact that I have never used a Mac for any kind of graphics work). Now, clearly, I am in no position to offer up an opinion about Quark's latest offer, luckily for us Dave Girard at Ars Technica knows both products and has offered up a very detailed review of QuarkXpress.
What does he think? Well, I can tell you that he isn't abandoning his copy of InDesign any time soon, but if you want the details you'll have to read his review.