First of all, Bravo! Siege of Spinner Cay is fantastic. I laughed my ass off in the beginning and then i got totally challenged by the game. Well, it's all logical stuff, which is good because it keeps you thinking analytically.
By the way, i LOVE the pirate with the huge scar and a fake eye, one of mcguillycutty's men.
I do have one suggestion though. Ever considered adding one more control on the character's faces as far as animation goes? the eyes and eyebrows move, the mouth moves and when you zone out playing, you start liking it, but THE CHEEKS never move. It kinda makes the characters look dead and that's also the same reason a lot of people complain about the repeat use of stock characters - because they aren't even really worth the repeat. I remember back in the good old LucasArts games that they reused characters, for example Bernard as the clerk at Stuckys etc. And I'm cool with that. Just make them look less dead.
As far as writing, really really awesome. It juices "classic Monkey Island" all over, and not just because of the references.
PS- It's awesome, the game works flawlessly on OSX via CrossOver! Hooray!