First off, if you're thinking that this is going to be another british type period drama with just a hint of realism, this isn't the series for you. Some scenes are VERY graphic and sometimes painful to watch (a woman is severely whipped for an offense while aboard ship....chaos reigns when the prisoners finally arrive in Botany Bay -- rape and violence). The conditions aboard ship while on the way to Australia are horrendous and graphicly shown. In other words, this is not a series for the faint fo heart. As for why the film makers felt the need to show such scenes, I can only surmise that they wanted the audience to experience at least a part of what these prisoners lived through.
Warnings aside, I have to say that I enjoyed the series as a whole. The actors involved were tremendous, especially Romola Garai (Mary Bryant) and Jack Davenport (Lt. Clarke). Romola managed to make me both hate and yet feel compassion for her character; a hard feat indeed. Mary, is manipulative to the extreme. She fought with everything she had in order to insure the survival of her children, her husband (fellow prisoner played by Aussie Alex O'Loughlin) and herself. The object of most of that manipulation is one Lt. Clarke, a man most certainly out of his depth and obsessed with Mary.
My one and only criticism of the series is that because of the way that certain scenes were shot and edited, you almost feel as if you should be rooting for Mary to end up with Clarke instead of the husband.
Overall, a definitely worthwhile viewing. High production values and beautifully shot. But be warned, this is most certainly not for the faint fo heart.