I would say about 85 % accurate in general, 15 % entertainment. On everyday life of Romans (and for that matter Marus Antonius' character if we believe Cicero), higher. On battles, motivations, characters, etc, less. As for their promiscuity, which offends many, Romans were promiscuous, and they are no worse than Danes or any other Western country.

Just like a computer game, a series like that has to cover some of the holes in our knowledge with assumptions and guesses in order to get the whole picture and thus an actual series or game. A TV-series also has to cater to the non-historians, and entain all the entertaining bits.

If you are interested, this book http://books.google.dk/books?id=Evww...age&q=&f=false, though getting on a bit in age is a good resource.