I'd say it's a pretty good return to form. Obviously it's no RTL or MOP, but it's pretty decent. Hated Cyanide the first time I heard it, and wasn't keen on the end of The Day That Never Comes, but in the context of the album they work very well, and improve on repeated listens.
The thing about the last few albums is that they very too straightforward. Metallica songs have always been about "parts", and stripping them down to basic verse/verse/chorus/verse/chorus/bridge/chorus/end just seemed to suck the life out of them (St Anger just repeated the same pattern twice in a row). Plus James' lyrics have been getting progressively worse. If there's one thing they've got right this time it's songs with parts.
Opening track is a banger, proper fast Justice-style stuff, with a few vocal nods to that album. Unforgiven III starts with some Nyman-esque piano before the Morricone-esque horns kick in, which I'm always going to back.
Overall vibe I'd say it's a mix of Justice, The Black Album, and a little bit of Ride The Lightning.
“Begin at the beginning,” the King said gravely, “and go on till you come to the end. Then stop.”