B
As far as "expansions" go, it's second to Stygian Abyss for me - probably only really down to it being a "booster", so there's less additions.
With regards the content given, for me personally, I was leaning A-/B+ direction. But, the missed potential dropped that a bit (along with the whole saltpeter thing for the first few weeks). There could have been more ships (Britannian, Elven, daemon... any group you can think of really), more variety with ship-based weapons (something like ballista and things).
Anyway, long story short, it's had a mostly positive impact on the game as I play it.