1) GM Ease of Play: 7. Because there are so many places the PC's COULD visit there is some homework but with the Isles of the Shackles book it's actually fun. Naturally some islands you may need to create on your own. There's also a ship combat system to learn.
2) Synthesis of the Story: 9. With the exception of book 4 it does a great job of this.
3) Role-play Friendly: 10 Plenty of opportunities and interesting NPCs throughout.
4) Combat Design: 10 again. Danger quotient changes her and there obviously but we had very few cakewalks and only a couple close-calls on TPK.
5) Fun factor: I had a 10 time running it and the group easily ranks it their favorite, 10 again.