I'm sure once they've worked on it at a few gigs and done it in the studio it'll all come together better.
Metallica are damned if they do and damned if they don't really. All their "fans" (that's people other than the millions who bought the Black album) want them to always sound like MOP, but if they always sounded like MOP then people would criticise them for always sounding the same ( a la Maiden).