It gets a lot of the concepts and settings right. The plots concerning Altair and Ezio were largely accurate. Except Borgia was an asshole til the end in actual history. But I guess they didn't feel like pointing out that not killing the bad guy can be REALLY BAD and how attempts to be the good guy are exactly the sort of shit that'd come back to bite you in the ass in the real world. So they just decided to make his equally historically terrible son into the bad guy for the sequel.
In summary, they get about as much horribly wrong as they get right. Although kudos for spoiling the big plot twist of AC3 in their earlier games. That's not something you see every day.
