I have finished the first season and LOVE it! I truly believe that those who love the story of King Arthur will enjoy this show as I did-for the wonderful portrayal of King Arthur's story.
Yes, it has some minor differences, such as a few names and characters, as well as some added storylines. But I'm enthralled by the characters that I've been attached to since the first season. Arthur is quiet, solemn, wise and humble, and Iain does a great job making you root for whatever he decides to do next. Guinevere is intelligent and compassionate, and compliments Arthur incredibly well.
Something rare to find nowadays is a show with a high budget, good acting AND a good script. If nothing else, this show has promise, and I hope people will see that as I have. Personally, the only fault with it is a personal grudge I have against shows that portray Christianity with inherant bias and bigotry, but I'm willing to extend grace and hope that they don't rely on making a religion a straw man enemy for the characters that we love.