I saw the 6-minute(!) trailer when it was online at io9 earlier today. Looks extremely ambitious, like the kind of film that could easily go very wrong. But I have no doubt it will still be a fascinating watch, due to the combined talents of Tom Tykwer (one of my favourite directors) and the Wachowskis (I'm still a fan of the first Matrix and actually quite liked Speed Racer).
Not having read the novel, the trailer reminds me of the similarly ambitious, but deeply flawed, Robin Williams film Being Human
. At least visually, Cloud Atlas will definitely be more interesting, though.