Void

First of all, Tyson living with percy and Sally and also percy knowing about Tyson being a cyclops: I like this change, I think that nothing is added by having this information be some big reveal in the first 10 minutes. Whereas Sally taking Tyson in and percy living with Tyson for a year, this all adds to their relationship between characters. It gives Percy even more reason to care about Tyson.

I think we can all agree that book clarisse is a completely different character than show clarisse. And I dont know, i dont think anyone was diehard book clarisse fans. She was written as a one-dimensional bully with no friends and next to no redeeming qualities, and I like to like characters. I think it's good, actually, that clarisse is more likable and sympathetic. I think its good that they are establishing early on why she might stay out of the major conflict in the last Olympian. I like that she's less of an unrepentant bully and more of an annoyed older sister who really can't stand her younger brother. (I agree that Dior is far too pretty to be playing clarisse)

I like that they're introducing the prophecy early on, I like how they emphasis it as this thing hanging over Percy's (and soon to be thalia's) heads. I like how they're framing it to be a point of tension between percy and Thalia, instead of the book reason of "posiden and Zeus dont get along, so neither do their kids". Because now its explicitly clear that both of these kids will know that the other MIGHT have the power to destroy Olympus.

Im currently unsure with how they're handling Thalia in general, but I had my doubts when they first brought up the great prophecy and since changed my mind about that.

Every other criticism I've seen seems to involve scenes that were cut or combined in order to save time. Classic adaptation stuff that I think the writers are handling pretty gracefully.