I finished the main story. It's been a thrilling ride, I must say, but not one without its faults. The meat of the game is amazing. Connor, in my opinion, plays better than Ezio or Alta´r ever did. He's more agile, has new tools and can freaking climb trees!
New York and Boston are great, but don't have the flair of Ezio's cities. These ain't no Venice, yo. But it's the Frontier that steals the show. Never mind that it's huge, but there so much stuff to do, so many animals to hunt, trees to climb. It's a marvel, never more so, in my opinion, than in the winter season, where the snow provides idyllic scenes where you can just lose yourself in.
There are downsides, though. First and foremost, the bugs. I have never seen an Assassin's Creed so buggy at release (and I purchased them all on day one, so I'd know), so this is pretty much inexcusable. Never mind the people sinking into the ground, getting stuck in the furniture or a horse that follows you around everywhere
that you can't even ride (this one's a real pain, as it messes up everything you do, from combat to certain quests), the real shocker are graphical glitches where half of the room is glowing purple and green stripes, parts of infrastructure that have a part sticking out across the whole room and more (granted, pretty much all of this happened in the underground tunnels, but it shouldn't happen).
The HUDs also quite messed up. Switching between weapons, getting to the Assassin Guild screen, it's all really messed up. Add to that the fact that some missions don't appear on the map and it can be a frustrating game.
AC3 is also inferior to the Ezio trilogy when it comes to its characters. Connor is as wooden as they come. Maybe it's unfair to compare the two when one had a whole trilogy to develop and unfair because nobody would ever match Ezio's flair, but considering you're playing the character for hours upon hours, I think we can demand a little more. The history figures are also pretty inferior to the likes of Da Vinci and co. in their portrayal. Achilles is a nice addition however. And, well, AC3 manages to deliver (in my opinion) the truly best character in the whole series so far, Haytham Kenway. You play as him for a rather long period before you get to play Connor, but it's more than that. He has a fascinating background (spoilers!), kills every scene he plays in (amazing voice actor, by the way) and
Lastly, and I've been in the minority that enjoyed Desmond's sections in the games before, I'm pretty disappointed about how it ended. He had some missions of his own that were an improvement (for the most part) to the previous games, but I always hoped for Desmond to come into his own and shine in some mad endgame, but alas, it wasn't meant to be. I know it's a bit much to expect the developers to drop Desmond in a complete modern city and do his thing, but that's a bit what I always wanted for the character. And it's really possible, you know, if they would only give themselves more time to develop the game and didn't choose a massive city to create. It doesn't have to be modern New York, per se
Anyway, hours upon hours of fun to be had in AC3. You need to look past some of its issues (and they're more noticeable than they've ever been in previous entries - the engine's getting old), but if you can (and a true assassin should!) then you'll have a blast.