Dimension Films, distributing the movie, pretty much just said, yeah, it’s delayed. Needless to say, some digging has turned up why, precisely. Fortunately it’s not because the movie stinks, or at least nobody involved thinks it stinks: This is the guy who turned out Planet Terror, after all.
I have been told that this delay is for effects work and not at all representative of the quality of the film or the confidence Dimension has in it. Robert Rodriguez is also notorious for how involved he is with the post production process and he has Machete Kills coming in September so I bet he just needs more time to finish the film.