I'm posting my first-ever review of a Paizo product to gush about how useful this product is. I've never been particularly impressed with the previous map folios, as they just seemed to be the maps copied from the adventures all in one place. The Rise of the Runelords map folio had a poster map of Sandpoint, which was valuable because the characters returned there many times (unlike the included map of Fort Rannick, say, which was the location for a few encounters, and the PCs never thought about it again).
Here, you get four poster maps which, laid end-to-end, provide a player map of the entire setting of the Kingmaker campaign and the basis for the PCs' kingdom. I taped the four maps together and laminated it, and it will serve as the centerpiece of the gaming table for the entire campaign. The PCs can write down locations they hear about, the changing borders of their kingdom, new towns, etc., etc. This mega-map will be useful throughout the entire campaign, and I can't imagine running Kingmaker without it.
I don't know whether the other two poster maps will be useful for much other than "here's where you are for the next couple of encounters," but they're basically freebies, as far as I'm concerned: the four-poster Stolen Lands map alone was worth the price of this product.