The maps in the full version give you the entire base, obviously, so that's one selling point. (That was enough to make it worth the purchase for me.)
The adventure is fairly straightforward, kind of a Night of the Living Dead scenario on the base with some twists, but it also includes some good flavor material to help get the mood right. If you're particularly familiar with the military you might get by without this, but it's good stuff in any case.
For reference, I'm planning to use the base as sort of an Area 51 scenario in my game, so the flavor is more to help me get my facts straight.