OK I have to start by saying I really do love what Paizo has done with 3.5 and taking the mantle of the RPG and raising the bar. I really do. And this book is good. But it's not great.
First, what's good about it.
The artwork is on par with the rest of the PFRPG line so far. In other words, fabulous.
The NPC builds of varying levels for each "type" of NPC make for a wonderful time saving device for GMs who know roughly what they're looking for and just need a quick and dirty set of stat blocks for the band of highway robbers that set themselves on the road the PCs are travelling down. On a related note, I also like the random tables for giving NPCs little quirks that make them memorable.
Also, each DMG type book you ever get has a section on "how to run an RPG" and I usually skim or skip those because I've been roleplaying for a long time. But there was actually useful stuff in this one for me.
OK, now the stuff that was not so good.
At times I felt like I was reading the Paizo product release catalog. I lost count of the number of times I was told in the first 50 pages how useful and wonderful the Combat Pad is for tracking initiative. I own the Combat Pad, and yes, it is cool. I get it. Miniatures, flip mats, modules, adventure paths, map packs, the crit and fumble decks, and so on. I get it - they're useful. But I don't like paying $40 for what at times felt like blatant advertising.
There are also what seem to be an inordinate number of typos and spelling errors in the book. Another layer or two of proofreading would have done wonders.
Overall though, more good than bad, and it's definitely a book I will use significant parts of. So I think 3 stars is reasonable. I could probably be convinced to do 3.5 but that doesn't exist, and I don't think I could give it 4.