The ending is obviously a setup for a sequel, but I don't mind, because they've been talking about the fact that it's a franchise since I've been hearing about it, and the historical storyline did get wrapped up to a real conclusion.
I've complained about the annoying shortcomings in the game, but the little cutscenes for the investigation meetings are pretty wicked. Although, it would have been nice to have explained that, when you steal info? You can access it via the pause screen, and it does things like show where guards are, and where scholars hang out, etc, etc.
But, this little exchange between me and the manager of game stop about the game totally captures the feel.
Gamestop Employee: What's the best thing about Assassin's Creed anyhow?
Gamestop Manager: You get to Shank A Bitch.
Me: No, no, no.
Me: Come-on. It's that you get to RUN UP A WALL, THEN Shank A Bitch. Duh.
 And that's hard. They're SUCH different games. SC just has that extra bit of coolness in keeping being fun.