I have it pre-ordered and have played a bit during this closed beta. It is pretty dang fun, but dreadfully boring alone or with a crew that doesn't talk.
I hear they plan to have a ton of content at release and down the road to keep things fresh and fun, but the core element in the success of this game will be the community. Without players to "pirate" around, this game will not last long after the novelty wears off of the main mass of people who bought the game.
After playing it for awhile, I am still very glad that I bought the game and am excited for release. I am very immersed in the environment tend to find myself talking and acting like a pirate. The sea and sea battles are second to non. The only thing I wish is that you could have more than a 4 man crew, which I heard there is a potential for them upping that.
Anyway, that is my experience and i am hoping to have more awesome fun times in the game.