I loved the first two books of this series and naturally had high expectations for the final one. Abercrombie is brilliant, Last Argument of Kings was as good as I hoped but in a different way than I anticipated..
The tone of the story stays the same, dark and grim and regardless of the fact that it happens in a fantasy world, it has realism in it that made me feel the sword cuts, smell the burning bodies and hear the death cries.
Only thing that bothered me slightly was the ending that left too much open. I liked the fact that the door was left ajar for new stories but with some things I would have liked to see less ambiguous endings. (This is the point about which I've seen the most negative opinions)
Abercrombie threw traditional fantasy cliches out of the window and made The First Law trilogy a great reading experience.