Things Sanderson excels at:
World building (overall), characterization, creativity, and plot.

Things he's sort of terrible at:
Language (get the man a thesaurus, the word 'stone' three time in one sentence? Really? And 'maladroit' starts standing out when you use it multiple times per chapter. Or paragraph.)
Pacing.
There are also a number of minor issues of continuity.
Also, I got extremely tired of Sanderson using child labor/cruelty to children every time he wanted to evoke pathos. EVERY TIME.

Then there's the fact that I still have no clue how women are regarded in this world. You have them being treated worse than male Skaa, what with the constant rape/murder by nobles threat, and in noble society they seem to be more or less where Victorian English women were as far as lack of basic rights went. Yet as soon as Vin gets out of her thieving crew, she'd treated like a complete equal by everyone. There's not even a breath of sexism. Not the tiniest hint, not even from servants or recruits. And you get the idea that Mare was treated the same way. Yet every other woman is next to faceless, and you don't get any dialogue from women other than Vin until 300 pages in. The biggest world building fail in the book.

All in all... I feel like the book suffered from length fatigue. Like, it needed a few more intensive editing sessions with a really good editor, but maybe its size prevented that from happening.
I enjoyed it overall. It was a good plot, and I liked the world and the mystery and the characters.
I'll read the next one, and hope that Sanderson improved by then.