Improved combat mechanics and a new setting do little to hide the flaws of this game.
The problem that seems to plague Assassins Creed III is that of an identity crisis; it wants to tell an amazing, historically accurate story, whilst still having fun gameplay that improves on that of the Ezio trilogy.
Firstly, the story of Desmond is boring as hell. While it does give closure to the end of the world in 2012 plot, it doesn't have as much power behind it as it did. As for the ancestors story, it starts as very interesting, but as you progress it seems to be consumed by history, until it seems to be a tourist guide to the American Revolutionary war, with Connor visiting events such as the signing of the Declaration of Independence for no justifiable reason. This meant that the story was very stop-start, as Connor would suddenly remember he is not in fact a tour guide to American history and is, in fact, an Assassin, one who has templars to kill.
Which brings me to the character of Connor, who is a one trick pony. Almost every one of his conversations begins with "Where is [insert name of Templar]?" to which the current historical figure of the day replies with something akin to "He holed up [insert historically significant location] you'll never be able to get to him" to which Connor will respond "I will kill [insert name of Templar] and prove you wrong" And then he does. His sole motivation for this entire endeavour is revenge.
Yes he does want to protect his village, but that just happens to coincide with his aforementioned motivation. Until one moment in the story where we take a tiny detour to remind ourselves that this isn't all about killing Charles Lee. Now I'm all for a good revenge story, but it must be accompanied by an arc, something to develop their character beyond "I wish to kill [insert name here]" And we do see some other characteristics to Connor shine through...in the side missions only.
Now the side missions of the Ezio trilogy were interesting; they gave us more to do, whilst still showing the Templars as bad and the Assassins as good. The side missions of Assassins Creed III tell us that colonial America was full of opportunity for the everyman, and that there was always money to be made somewhere. Do you remember having to upgrade the villa in Assassins Creed II, and then all of Rome in Brotherhood? Well now you have to create a town, by settling people of various backgrounds down to help around the place. Most of them help by allowing you to create unique weapons/upgrades, but then you get to settle a priest... How does that help with being an Assassin? It doesn't, he's just there to provide moral guidance to the people of the town, as stated by the game after you settle him.
But what about that characterisation I mentioned? Well Connor makes friends with all of the townspeople in the course of a few days (including making friends with a lady who get pregnant and gives birth in the space of about a week (great realism that :D)) and they have some nice interactions, however fleeting they may be.
There are also missions to deliver letters, hunt myths, hunt animals, beat people up (but only specific people and only with your bare hands), hunt items, assassinate a few dudes and sail about on your own private ship.
Yeah you heard me, you have a private ship with a full crew and you get to have naval battles...that's pretty damn awesome. This has got to be the best addition to the series that this game has to offer, and it is done very well. I enjoyed having to manage the steering whilst ensuring I was in a good position to attack an enemy vessel. But there's very little else to it really.
The game also gives us a better set of combat mechanics than we've seen in previous instalments, in other words while waiting to simply counter an enemy is still a viable option, there are a lot more things you can do that will work.
Overall, Assassins Creed III has a weak story, weak characters, good combat, great naval gameplay and mediocre gameplay. It's good while it's there, but after a while you start to realise it has a lot of flaws.
Oh and the multiplayer is pretty good, give it a try.