Besides Quark's business practices (which seem to operate in a separate universe...this is the company that, after Apple removed floppy drives from their product lineup, still shipped software that required you to insert a floppy disk to install its product), I've always been boggled that Quark files are proprietary by their nature. If I could export a Quark document out of InDesign, or export my Quark document into Illustrator, life would be oh so much simpler for everyone.