That something billed, on any level, as an Alien prequel would be expected to veer away from horror is - well - puzzling.
That said, in retrospect, the buzz from last year or so, reputedly from reliable sources (i.e., from Scott himself) and to the effect that Prometheus would not be a true Alien prequel, now pretty clearly seem exactly like disinformation, perhaps for the purpose of misdirecting to get maximum surprise and enthusiasm upon seeing this trailer.
I'm rather encouraged by how much the 1979 film seems to be having an influence on practically everything shown in the trailer.
That said, I'm only cautiously optimistic. Part of the angst and charm of the 1979 film is in the derelict, and the story behind how the Nostromo came to be sent to the then unnamed planet, both being mysteries. There is additionally a risk that, when details are painted in, they will not live up to the inevitably rather high expectations. Generally speaking, any new film can disappoint, but most especially when the expectations are that a film will be the most awesome experience in theaters ever. I say this mainly from having been disappointed before. I'm thinking of you, The Phantom Menace.
I hope for the best, but in any case, I'll certainly be more than satisfied if this is better than both Alien 3 and Resurrection.