Ridley Scott's latest work hasn't come close to what he previously achieved with Alien and Blade Runner. Gladiator is all right even though I've never been able to stay awake through the damned thing, but Robin Hood was abysmal despite having an amazing premise in one of its earlier drafts (which supposedly followed the Sheriff of Nottingham as the hero before Scott told them to Hood that shit up). So, I generally don't get excited anymore when I hear about any new projects that the man is working on.
This is where I turn this post around and start talking about Prometheus and how it completely redeams Ridley Scott for G. I. Jane.
I love the Alien series and, as such, am also hugely excited for Prometheus. No matter what anyone else has ever said, Prometheus is undoubtedly a prequel to Alien and this trailer finally proves that. Even the title animation is the same, with each letter fading into view one line at a time. There's a pilot seat that's identical to the one in Alien where the crew of the Nostromo finds the Space Jockey, and even the vehicle designs are reminiscent of the Nostromo, Sulaco and the military ground vehicles from Aliens.
What is unknown is if this Alien prequel will have any of the titular xenomorphic aliens that have chased Ellen Ripley through space over the course of a few centuries. Personally, I don't think it will, barring some minor cameo where we briefly see a facehugger in stasis.
My personal theory about Prometheus is that the Space Jockey's ship seen in the trailer is a vessel carrying many different species (possibly contained in the pods which are placed before the giant effigy of a human face)—the xenomorphs and possibly even humans among them. The premise of the film, after all, is that the human crew is searching for the origins of their existence. Maybe the Space Jockey race went around scattering the seeds of life around the galaxy. It sort of ties into the theory that the Earth is just a big petri dish where a vastly superior alien race is experimenting with creating primitive lifeforms—sort of like what we're currently doing by creating synthetic organisms, which I think is an unbelievably cool scientific development.
Anyway, one last observation that I'd like to make is that the logo on Noomi Rapace's forehead (the actress playing Elizabeth Shaw) toward the end of the trailer looks a lot like the Y portion of the classic Weyland-Yutani logo (see the coffee mug to the right). In the Aliens vs. Predator films—which I'm hesitant to call canon, but they suit the purpose of my speculations—we're introduced to both Bishop Weyland (Lance Henriksen) and the head of the Yutani Corporation (Françoise Yip, credited as playing Ms. Y), indicating that a merger occurred at some point between then and the time that Alien is set in. So perhaps the mission in Prometheus is being funded by a pre-merger Yutani Corp, which gives some hint as to how long before Alien this film takes place.
If you want more details from the trailer, here's a scene-by-scene breakdown by io9.

