I thought The Borgias was excellent. I would give it four and a half stars only because I agree with the criticism that there are too many gratuitous sex scenes. We get the idea already, the pope had a mistress, Cesare and Juan were sleeping with their brother's wife, etc.
From the first episode, with its long shots of processions and so on, I realized The Borgias would be boring for people not interested in the period or at least with history in general, but if one is interested in either I don't see how you couldn't enjoy it. The sets and wardrobes are amazing. The production is lavish. The acting is great. The casting is good. Jeremy Irons is superb--the subtle (and sometimes not so subtle) changes in his expressions indicate his thoughts, mood and burden. His is a very convincing, though not very spiritual, Alexander Sextus. Cesare's performance is excellent and the portrayal is refreshingly sympathetic, yet still nuanced. All the performances manage to exhibit economically the psychology of the people. The dialogue, formal language and diction are compelling and entertaining (love all the conditional tenses).
I would wish they could have followed history a little more closely but understand the need for compression, and nine episodes for two years is already generous. I've read a lot on the period but this helped me to get some things that didn't sink in from reading books, like just how monumental the invasion of Charles VIII was for the Italian psyche. How it inspired Alexander to increase the power of the papal states. How it affected the thought of Machiavelli and others. How it helped give birth to the balance-of-power concept. The series also conveys how much the Borgias were looked down on due to their Spanish roots and how the children had to deal with the stigma not only of being illegitimate but also of being the children of a courtesan. The movie also makes it sink in how long Cesare was a cardinal--and how much he hated it--before he became the infamous Duke Valentino.
Looking forward to the next season.
There are many small historical inaccuracies for the sake of compression and drama. One I would like to point out is that it was Lodovico il Moro of Milan who proposed to Charles VIII that he assert his rights to the kingdom of Naples; Ludovico did so because he was worried that King Ferrante of Naples might assert the rights of Ludovico's nephew to the dukedom of Milan; it is, however, also true that della Rovere went into exile in France due to his hatred and fear of the Borgias and further encouraged Charles VIII to invade Italy.
The old French King (Charles VIII) is a great character but was actually only twenty-four at the time.
Also Machiavelli did not become Florentine Secretary until 4 years after the French invasion, at which time Florence was a republic.
Lucrezia was only thirteen when she married Giovanni Sforza.