It's kind of funny, I am very picky about the Player Companion line, and this product is one of the few I have picked up.
I really liked having flavor text for Pirates from different regions of the Inner Sea, as well all the specific traits, it will help make your pirates different from one another. The Freebooter seems awesome, if you going to be in ship to ship combat often he's going to make a big difference.
The pirate code and slang pieces are nicely done, and the information about the ship flags.
I can see how it diminishes the value of the product if it collects information from other sources, which seems to be one of your main complaints, but if one doesn't own those books, it's a great deal. I know there is overlap between players and GMs, but I don't think I would buy an AP episode just because it contains 1 or 2 pages about pirates either, that seems like a worst deal if you don't intend to buy the whole AP.