Cross-Platform Desktop Publishing Recommendations

Grace asks, "Is there a desktop publishing application that's compatible for both mac and PC?"  As Phoenix replies in the forum, programs such as InDesign come in both Mac and PC flavors and can share files cross-platform. But, when money is an issue (such as for a school or a small organization), Scribus is the open source/free alternative. What would you recommend and why and what issues might come up when sharing design duties across platforms?

And speaking of Scribus... it's one of the finalists in multiple categories of the About.com Reader's Choice Awards. Check out the competition and tell us who has the best for software graphic design, personal projects, or in the category of free desktop publishing software.