I thought this was a good episode, but kind of slow-moving. Too much time is spent building up to what we have long known is going to come. A few observations:
This episode further doubles down on the project of making Rhaenyra and the other Blacks (with the possible exception of Daemon) as sympathetic as possible. Rhaenyra does everything she can to avoid large-scale war, short of surrender, including even risking her life to sneak into King's Landing to meet with Alicent. Show Rhaenyra is vastly more admirable than book Rhaenyra.
By contrast, Aegon II looks like an even bigger dolt than before (this is consistent with his depiction in the book).
After hearing Rhaenyra out, Alicent begins to doubt her son's claim to the throne, but realizes it's too late to change anything. Yet she misses a chance to end the war by calling her guards and having them capture Rhaenyra. Once the latter puts away her knife, Alicent can probably do this without getting killed herself. By letting Rhaenyra go, she ensures a much higher death toll, regardless of who wins the war. This is the counterpart to Rhaenys refusing to wipe out the Greens with dragon fire when she had the chance at the end of Season 1. Both these episodes of questionable forbearance are NOT in the book.
It was stupid of Daemon to take Harrenhal all by himself. Yes, it works. But he is incredibly vulnerable there. IIRC, this is at odds with the book, as well. But I could be wrong.
The Blacks should just wipe out Criston Cole's army, while it is exposed and they have the edge in dragons. He was stupid to march out with no dragon support, and Rhaenyra makes a mistake in not heeding her advisers' pleas to exploit that error. I guess this is true to the book, as (for the most part) neither side is competently led during the war.