Brad's posting and info on how 64-bit maps will be able to be huge is beneficial in two main ways:
1. Games can last and be as long as you'd like (duh). Talk about epic!
2. The even bigger benefit is this- better controls for empire management and tools for reducing grind/micromanagement.
I really believe that when the GalCiv2 devs added an enormous galaxy size later on in the game's life cycle, it uncovered some of the nagging flaws that were amplified on a massive scale. Mainly, the amount of micro-management required and the need for more automation/control on a global scale.
Can you think of other nice benefits to the really, really, really big maps?