My two cents on this one. I don't own this set, so all of my opinions are based on looking at the completed set in pictures and at the store, and going through the instructions and brick lists online, so take this with a grain of salt.
I'm generally not a fan of molded boat hulls. You may have noticed that every time I comment on a MOC of a ship I always rave if they've come up with a good hull shape using normal bricks and plates. I'm much less likely to comment if someone uses the pre-made hull pieces. In addition on this ship I think the ramming projectile at the front looks odd.
I agree with Steve on the fig inclusion. If someone is buying one of the most expensive sets in the line, LEGO is reasonably safe in assuming that they have purchased several of the cheaper sets, so they're likely to accumulate multiples of the 'hero' figs. So maybe it would make more sense to include additional special figs. Of course the flip side of this logic is bad for me as someone who is more likely to buy a few of the cheaper sets and less likely to buy the big ticket set, so I'm less able to get the exclusive figs. Perhaps the answer is to include repeats of the hero figs, but with alternate torsos. So a completist collector would still want to get the versions in the larger, more expensive sets, but many of us would be happy having one version of Gimli and not need Gimli wearing chain mail, Gimli with a cloak over his chain mail, Gimli without mail, etc.
All of those shields make a great inclusion in this set. They make a nice detail piece on the boat, but can then be repurposed to create a custom faction.
Of course they included a catapult, but this one looks pretty nice.
Anchor made of an axe is a cool detail.
I love those sails, though there should be strings for rigging.
Biggest failing of the set, IMO, is the missing banner. I don't remember if this is in the movie, though, but the big moment in the book is when everyone is despairing because the black ships of the corsairs are coming up the river, and then the banner of King Elessar is unfurled, revealing the final turn in the battle. Even if this wasn't in the movie (I'd have to go back and check), they've included book details in sets before, like the portraits of the five wizards in Orthanc and the Palantir stand at Weathertop.