Recently got the book and after a quick read-through: It's a very complete, solid book with lots of crunch (for both players and DM), but also lots of ideas and useful info for the DM (especially liked the cargo lists, distance tables, village complications, and the stock NPCs -- we need more of these!).
On the negative side, I would (like many others have commented upon) have liked to see a few maps of one or two port cities (Khemi, Asgalun, etc.) and maybe some maps of ancient/lost/treasure islands and pirate hideouts. Although these are not too difficult for the DM to invent for himself, some "professional" maps could perhaps have provided some examples and ideas for the DM to build upon.
Also, there are one or two rather non-Conanesque pieces of art, such as the woman on p. 35 and the pirate on p. 14 (although this latter one could pass as OK, I really feel that the artwork in the Conan RPG books should be more grim and gritty, such as the pirate on p. 66 and the monster on p. 99). The NPC illustrations (by Quilliams) are top-notch.
Overall, I would say it's a 4.5 out of 5... because it does exactly what it's supposed to, expanding the options for naval/pirate campaigns in Hyboria and providing a wealth of inspiration.