I've been playing this for a little over a month now and it's been worthwhile in some ways, a huge waste of time in others. Like any MMO, at some point your going to need to grind your skills. The combat is pretty lame, as is the water effects (ie storms and such). On the up side, you can travel to ports all around the world to trade or search for treasure, or to just mix it up with some generic pirate types. There is PVP in select areas throughout the world that are designated hostile waters. All of Europe, which is where all players start out, is designated safe waters, so you can level up without worrying about someone griefing you on your maiden voyage. There is the option to join a company, or start one of your own, if you feel the need to be part of a clan.
This game has been around since 2005 in Asia, but only launched it's English servers late last year, so things are still being developed. Man, I can remember playing the NES game Uncharted Waters that this game is based on...
"We're here to tell ya that we're out to get anyone from Portugal"
At any rate, if you don't mind some dullish combat and sailing from port to port (no quick travel) then this is a pretty decent way to blow out a few hours a night.
Oh yeah and it is free, with no annoying advertising, so that's pretty cool!