Overall this is a pretty good game, with some good points and some bad points.
First of all the good points. The game is gorgeous to look at (especially if you have a decent graphics card) and you can live out your fantasies of being a pirate in the seas around the Carribbean, even though the ports are ficticious. You can attack other ships with cannons (or just board them) and plunder them for riches (such as gold, spices, luxury goods, cannons, etc), recuit more men for your ships from local taverns, carry out missions for different sides (the Spanish, Dutch, French and English) and find buried treasure, amongst other things.
I think that plundering ships and finding treasure are the easiest and best things to do in this game, there are occasions where you might have to fight the captain of the ships you attack on the deck, but its dead easy to win the battle usually. Its a bit more difficult when you go up against another pirate, but still relatively easy.
The game generally is about becoming the best pirate by working your way up the ranks, making sure your crew remains happy (as bad crews can become mutinous and leave your ship) and gaining as much wealth as you can. Although there are some diversions from time to time, such as dancing with the governer's daughter (of whichever port you are in), which I personally hate doing.
You can repair and upgrade your ship as well to make it last longer in sea battles, make is go faster and more maneuverable when turning at sea. You can also get tips and hints from the local owner and busty wench at the various taverns, as well as items to help you in various ways from the 'dodgy guy' in the corner.
The downsides to this game are (as I have already said) the dancing part of the game, although I can imagine some people will like this part, the fact that if you are sailing against the wind at sea, it takes several minutes (or in game time being several months) to get to the place you want to go and that's a real pain in the a***!
The other gripe is that the sea battles can sometimes last aaaaaaaaaaaaaages, often going well into night-time by the time you're finished and the aiming isn't always accurate, plus the treasure hunting expeditions on land can get a bit annoying. You could be walking for ages without even getting close to the treasure, but at least its clearly marked when you get there.
Generally speaking this is a fun game experience, with gorgeous graphics, authentic sounds (like booming cannonfire) and a bit of swash-buckling, which is unfortunately let down by what I think are some annoying add-ons and distractions. You might like them.
A word of warning though, this game can suck up a HUGE amount of your time and can get quite addictive, many hours can pass without you even realising! If you don't mind that, then I can recommend this game.