It's an inconsistent book. It doesn't have every item in it (it lacks the Grave Candles from Council of Thieves for one), and displays, at times, some appalling editing. Its use of the format from the Beginner Box also makes some of the entries look dreadful. The colour choice for rings is unbelievably bad.
Also, it looks like Paizo skimped on the art. Having some entries have artwork next to them while not next to others isn't good. There's no rhyme or reason to it (I expect it's because they've done item cards for some items but not others).
They've revised the magic item generation tables significantly. (As such, the book doesn't work as a source for stocking cities; we have to wait for the Ultimate Campaigns book before that part of the revision is done). I'm not really a fan of having the random tables spread throughout the book, but at least there's a table for the TYPE of weapon or armour now.
What I really dread about the book is that Paizo will take it as another excuse to not include stats for items in adventures. More and more, Pathfinder modules can be played if you have a computer with access to the internet, but otherwise you need an insane number of books to play them... and I'm not a fan of this trend.
Otherwise, the book looks fine, but it's really hard to tell how useful it is until I've used it a lot more in play. At least it makes it easier for me to find the poisons.