I think I fucked around out of order, because I did a load of rebuilding Rome before the game informed me that I was able to do that. Oddly, I'm enjoying the extra gunk thrown into this one, as opposed to in AC1 with the flags and AC2, where I did enjoy the side quests at first, but eventually ditched them and just went through the story. I don't like that landmarks sit there with their giant price tags, making you think they're worth something, when really they're just to have. That's 29,000 florens I'll never see again.
As for the story, I just got to the point of recruiting assassins last night. Deploying them is beautiful. A Borgia knight moved past a haystack on horseback while two foot soldiers marched behind him, and then two of my recruits pounced out of the hay, killing one soldier outright and yanking the other into the hay with a knife to his throat. The knight kept moving, completely unaware.
I kind of wish Ezio had some part in training them though. You see them on the street, you help them fight soldiers (which felt like saving citizens from AC1, which I missed), and then you send them off. Instantly, they're available as trained assassins. I would've liked to have done stuff with the first batch, showing them the ropes.
In case anyone didn't know (I stumbled upon it by accident yesterday), the PS3 version has some free DLC: two multiplayer maps, and an extra layer of side-quest stuff for the single-player involving rescuing Copernicus and his scholars from the Borgia.