I've listened to it a few times now.
Yes - there's a definite Diamond head tribute going on, but with a very motorhead influenced rhythm.
James' vocal was challenging on the first listen, but I'm actually hoping the rest of the album has this slightly more NWOBHM/ early thrashy feel.
I think that because Metallica have had success with different groups of fans over the years (setting the standard for a lot of thrash/ radio metal/ accessible rock ), there will always be divisive opinions.
I'm totally prepared to give the album a chance when it's released in the hope that a) there's not loads of filler involved, and b) it's not half assed and crap lol