All I have ever heard about Zeta was that it was a hallway shooter. That is very true. It is primarily a hallway shooter with unengaging enemies in a surprisingly lackluster dungeon, aesthetics wise.
However, what has made this DLC shine more than any other DLC and even the base game is the NPCs and stories associated with them, as well as the recordings found in the prisoner logs.
But to get to the short and sweet: in no other DLC besides, possibly, Dead Money, is there as much story reactivity, NPC interaction and a progressive alteration of the environment. That is, the NPCs actually interacted with eachother in meaningful ways. You could interact with the environment via the NPCs, which had gameplay repurcussions. The NPCs had their own motivations, and weren't just simple yes-men automatons. A perfect example of this is if you go with Elliot to the Cryo-Chambers, he activates many of the static objects on his own volition, and we see the playing out of his own storyline through that section of the ship.
The way that each NPCs reactions to eachother, to you the PC and to the environment around them as you progress through the admittedly limited gameplay (go here blow this up) has made this by far the most engaging Fallout 3 story to me, period, without competition. Notice how the NPCs go and make a home for themselves in the central hub. I can't think of anything even remotely similar to this in Fallout before. The way that the environment went from sterile to lived-in just doesn't happen anywhere else.
It seems so minor, but when you notice this level of interactivity it makes a lot of the rest of the game feel very hollow.
The way that everyone has a line of dialogue or five for basically every new event, or as with Paulson, with every new advance through the Hangar Bay, is again, a concept not touched in the slightest until New Vegas where the companions were much more fleshed out and actually reacted to the world around them. It makes going back to vanilla 3 NPCs such a stark wake-up call because they are so flat, lifeless and have zero agency of their own.
One last, but not minor thing is again, the NPCs reacted to eachother! The fact that Togo disappeared was something everyone noticed and you could comment on. There was a social milieu in this small family they were building. As in, these were characters cognizant of a wider social context and not just, as is typical in Fallout gamebryo dialogue settings, two people interacting in a stale microcosm where no one else exists outside of their scripted interaction and if everyone dies around them, they just respond with "hey, what can I do for you?" after the death of their entire extended family.
Does anyone know what i'm saying here? And if so, is there anything else like this level of interactivity and levels of development like this? I loved the idea of being part of a small team coming together, getting to know eachother and changing the environment around them and who seemed to have a dynamic of their own independent of you. The conversations the NPCs had with eachother were not "Rothschild, how is the development of the Advanced Recon Suit going?" level of triteness, i would always stick around to hear what these people would have to say to eachother.