I got this for Christmas and have played about 14 hours so far, it is challenging and hasn't got repetitive yet, there is so much to do in this game.
The game is ideally suited to the PSP, the controls are superb, very simple and I like that you can save the game almost anywhere. Making it easy to pick up and play whenever you feel like and not having to worry about finding a safehouse before you get off the bus.
The graphics are decent, nothing amazing but they do the job well. It would be nice if there were cut scenes and not just dialog along the bottom of the screen but that is my only grievance, well apart from wind effects whilst sailing but you get used to that.
The game has so many different gameplay styles meaning there is something about Pirates you will enjoy. You get to take part in dancing mini-games, search for treasure whilst avoiding traps and predators, collect maps to reveal your next objectives, sneak out of prisons, lay siege to towns and most importantly, you get to attack shipping in the Caribbean, depending on what you need you can attack merchant ships/pirate ships/frigates/transport ships/canoes.
All in all a very enjoyable game, definitely worth a purchase.