I find the whole subject of “liquid layout” intriguing:
Use alternate layouts and liquid layout rules to optimize your portfolio for the vertical and horizontal orientations on the iPad. Learn about the Adobe Digital Publishing Suite workflow and how to prepare your portfolio for the iPad.
The “liquid layout” features (some of which have been available in comparable forms in application development IDE’s for many years) are truly game-changing inside ID. Especially taken collectively. The ID developers did a great job of leveraging existing architecture, too. (E.g., the alternate layouts are really just “more pages” in the document, and segments of pages are used as “parallel” documents within the ID file itself.) A tremendous amount of convenience and flexibility was achieved with a relatively small amount of architectural modifidation — this kind of sweeping new capability could have been done in much, much more complicated ways, to small (if any) advantage. What strikes me most about the whole implementation is how SENSIBLE it is. Time will tell what may still be needed, or need to be done differently, but it really solves a ton of problems in use-cases from eMags to eBooks to simultaneous PDF & print, and a lot of others.