I agree with much of what ColortheHours048 said regarding the Sorkin rewrite. While I appreciated cutting the dreadful Nimue number, and I liked more given to Mordred's backstory, I find that many of his contributions detracted from the show for me - the modern verbiage, the need for characters to cut each other off with the little witticisms, and he is so very on the nose at times. From the moment we see Sirs Dinadan, Lionel and Sagramore when they first enter the stage, you go "Bad Knights!" :/ If one more person said "Things are changing TOO FAST around here..." We get it.
I will be an outlier and say that I was not crazy with Phillipa Soo's portrayal of Guinevere. She has a lovely voice, but she was so adversarial through most of the play, that by the end when she tells Arthur "I loved you from the moment I met you and you sang that silly song", I thought, "Really?" She spent much of the play glowering at him or distant from him. And I get that there is a divide there, but I never felt terribly sad when she fell in with Lancelot because I never got the impression that she liked Arthur very much throughout. I also did not really buy into the whole "We have a 'partnership'" dialogue that seemed to put her over the edge, along with the 11th hour Morgan Le Fay discovery of Arthur writing her letters. "What Do The Simple Folk Do?" should show the sad decline of their marriage, and frankly, it never felt like it had much to decline FROM as it pretty much dragged from the start. I am not sure if that was Sher's direction, Soo's interpretation of Guinevere, or what, but she just looked either angry or flat a lot of the time, other than the Lusty Month of May song when she really came to life.
I liked Andrew Burnap's Arthur very much, he has a fine voice, and I think he brought a boyish charm to the part as well as the regret at the end when he realizes that his marriage is over and his kingdom falling. However, Sorkin again has him say he blames himself and Jenny's father for forcing her into the marriage contract. If HE indeed forced that point, why then at the start of the show is he saying how much he is terrified to marry her and reluctant? Doesn't quite track.
Jordan Donica was a wonderful Lancelot. Terrific voice, and I did see the regret in his face, mannerisms, and gestures as he struggled with his devotion to Arthur vs his attraction to Jenny. I think he made for a great counterpoint to Andrew's Arthur, and you LIKED both of them, despite Lance's initial arrogance. He brought out the humility in Lancelot in several scenes. Particularly liked the fight scene choreography with the knights, though why have Arthur step in for Sir Sagramore? In the original, doesn't Lance actually seem to bring Sagramore back from the dead through his pious prayers? In this, Arthur seems to turn it into a joke - "I was UNCONSCIOUS!" which undercuts Lancelot's "miracle" which brings so many over to his side.
I thought Dakin Mathews did a good job with Merlin / Sagramore, and Taylor Trensch was a strong Mordred (and I thought he did a great job of playing that part younger than Arthur). The orchestrations were gorgeous and I enjoyed the use of lighting effects from the snow to the thorns growing around Morgan's house. The scenery they did use was lovely, but I agree that the stage looked too empty and vast at times - a larger chorus and a few more set pieces would have helped a lot.
Overall this was a mixed bag for me, which was the same reaction I had to Sorkin and Sher's "To Kill A Mockingbird" - I felt that a few of the updates in that (like the expansion of Dill's character) were wonderful, but a good bit of the updated dialogue fell flat and some of the characterizations did not seem true to the original material. I felt the same here. That despite the gorgeous music, the strong cast, the moving story, that some of the revisions were overdone. I wanted to love it, but came away only liking a lot of it, and I am feeling like it was the production team more than the actors and musicians that let me down a bit.