It's a 3,5 for me, and it was more like a 3- for most of the book but the ending saved it. There's so much political talks and plots and stuff, until, like, page 600... And then finally the action starts as well as what I (we?) had been waiting for. It's too bad all the revelation have to come in the last 10 pages. I would have preferred for some of them to be more scattered through the book. 
 Some passages really dragged for (still) no apparent reason and it feels like 100 or even 200 pages of this book could be removed without loosing any character or plot development. 
 Anyway, the ending was still great. It kind of made up for everything else and also it leaves off on a real cliffhanger, which really lacked, in my opinion, at the end of book 1... 
 Also I really hope we see Tensoon again in book 3. 
 Side note : Vin and Elend annoy me to no end which might be a problem for the future.