These Americans/Canadians are really stepping up their game with how TV series are shot. There's Spartacus, Camelot, this - all with presumably large budgets and tackling folklore or historical fact in a way that was only ever seen in a movie previously.
Not everyone will love this show - it's really not that graphic (in comparison to Spartacus: Blood and Sand/Gods of the Arena) but don't tune in hoping to see a whiter than white Pope. There's sex, violence, plotting, battles, etc. Basically a reasonably accurate depiction of life during this time - the Pope was 'king of kings' and Borgia was all about gaining power by trying to bribe others or marry off his family into the different Italian provinces.
As someone else said, Jeremy Irons is ok. He plays the role in a very subdued way, he's always very contemplative but I quite like it.
It's very interesting as I previously wasn't too aware of this period in time. From the Wikipedia entry on the House of Borgia, it would appear that the producers have taken some artistic licence as Giulia Farnese and Lucrezia were actually a lot younger than is portrayed in the show.
It's all very cloak and daggers - religion is but an after-thought and way of keeping people under control.
The series ends well with the promise of more but it seemed to accelerate time quite quickly towards the final episode.