I'm in 100% disagreement.
The trailer sheds light on a subject that's been somewhat untouched through the main narrative of the Halo series. The main narrative meaning the straightforward story provided by the game's missions, cut scenes, and dialog.
It brings up the subject of humanity, what John actually is. Throughout the previous games you're touted as a an ultra-badass; the perfect soldier. Arriving at the front lines you're greeted with dialog praising your arrival, but while you may be the "perfect soldier," you're an imperfect human.
I love the dark themes being twisted into the Halo story now. The fact you're a kid who's actually a science experiment originally bred to kill his own race is fucked up.
Who in their right mind would be okay with that?
Who could live with that?
Now, look at the way Chief is being suspended in that blue field, the way he's held prisoner there. It's kinda Christ-like isn't it? Now draw the parallels. Regardless of your religious affiliation, the story of Jesus is equally torn. You grow up knowing you're the savior of mankind... but you're also just a kid; a human being, with feeling, with emotion, and with a moral gray area that we all can identify with.
You're the Atlas of the world. The fate of your entire race, a race you might despise because of what they made you, rests on your shoulders. Would you just be cool with that?
Now let's look at the tagline of the trailer, "An Ancient Evil Awakens."
At first inspection it looks to clearly refer to the Didact, or whatever your main adversary in the upcoming Halo title turns out to be, but I urge you to dig deeper.
What if the "ancient evil" is actually what's inside John, an evil within himself that he's suppressed. A distaste for humanity, for his own humanity, for what they made him and what they made him do.
If you're at all familiar with Freudian psychology then you'll be akin to the ideas of the id, ego, and superego. Imagine Cortana is the Chief's superego, the dialog that works between the id and the ego. As Cortana deteriorates and goes rampant, the Chief's consciousness, his ego, will be directly exposed to his id, or our instincts that don't care about reality or the needs of others, only its own satisfaction.
Maybe he's not the "strong, silent type." Maybe he's the type that's biting his tongue from telling his superiors to fuck off because he never asked for this.
If you're just staring at your computer screen letting the images flood your brain while you sit there flat lined, yeah, this trailer seems hokey. However, use that brain thing inside your skull and it becomes this dark undertone that's been present in the Halo universe, but never indulged in the games.
That's why I'm excited for Halo 4's campaign.