Give it a chance! This show takes some getting used to (especially if you come after more lavish Showtime production). The first few episodes are heavy with exposition, the mishmash of accents can be jarring and the young Borgia are immature and not very likable. However, it quickly becomes obvious that this is done on purpose: after all, the brothers, Cesare and Juan, are still hot-headed teenagers eager to prove themselves while Lucrezia is just a child. During the course of two seasons, through trials and tribulations, they grow and mature, and Cesare is very believable as a flawed character with conflicting motivations, and the force to be reckoned with, just like his legend suggests. Cesare and Lucrezia not only do they look like their portraits, they are doing a terrific job bring their complex characters to life.
Other cast is superb, too, even Doman, who might lack Irons' expressive voice but brings commanding presence necessary for the most influential man in the Christian world. All in all, the character development is one of the best I've seen on TV (worthy of anything on HBO), even the minor characters seem like real people with their own agendas rather than just the talking heads. This show is also truer to showing life and times: St. Peter is run down, just like it was, in all the night scenes it actually looks like the world lit only by fire.
As far as historical accuracy goes: remember, most of the dark deeds attributed to Borgias are due to the smear campaign of their enemies. I doubt that the real Borgia were really much worse than any other noble family squabbling over Italy at the time. I think Fontana successfully combines some of the legend with the actual historical events, not without some dramatic license, as expected. There's a wealth of details that makes Showtime's show look like Dallas in period costumes. After a somewhat shaky start, it became my favorite adult historic show since Rome.
