Well, it DOES have Johnny Depp AND Helena Bonham Carter AND Sascha Baron Cohen.. so it's pretty much guaranteed to be a great film, but check out the Sweeney Todd website for updates.  Apparently it's quite violent and they've had to edit it several times just to try and get a rating! 
I am so excited to see this!!  Jeez, between Westerns and Dragons and Zombies and Revenge-seeking Barbers, I have a full movie season!