I was shocked to see the number of one star reviews and can distill them as being unhappy either with the amount of sex or because it's not "historically accurate enough."
The whole point of the series is that historians do debate what the relationship was between James I and George Villiers, and tells the story of one side of the debate. It's very entertaining for what it is, and a quick Google search can easily show what parts of the plot are up for debate amongst historians and where they took more artistic license. As a drama series it's entertaining with great character development. If you're not put off by some gay sex scenes, it's a great watch.