Really there are two times I can see that the "live" part of live tiles are used:

  • When a tablet is docked and its main purpose is to sit on the table and look pretty while displaying live data via Start screen
  • When checking aggregate information during the course of normal use

Microsoft could do a bit better in both of these areas, in my personal opinion:

  • Allow live tiles on the lock screen (touching them would prompt to unlock), so I can keep the tablet secure but still gain the benefits of live tiles
  • Allow the start screen to sit in a snap view, so I can see live tiles without moving away from my current app