The layout programs like InDesign or Quark are most useful if you have a lot of major graphics or layout issues: wrapping text around odd shapes, combining multiple layers of elements, layout out text shaped paths. Also, if you're doing a magazine-like layout where you have stories jumping across discontinuous sets of pages. And, of course, they're great for dealing with printing masters for folded booklets, since it handles all the pagination issues automatically, and they have a lot of built-in tools for communicating very precise printing specifications for when you're dealing with something higher-end than a desktop printer..