The demo basically covers the first 2-3 hours of the game. You'll get to explore the first two floors and a small part of the third floor of the main labyrinth; and you'll get to explore part of a floor of another dungeon.
Hold the phone, why haven't I heard about this yet...another dungeon? There was only one dungeon in EO1. Even if there's just mini-dungeons like in EO4 that's still something of interest.
As much as EO1 is my favorite, I burned out just short of beating EO4, so I'm looking for any tidbits like this that might sell me on the remake sooner rather than later.