The sound effect for the Head Key is definitely amazing/awful.
I finished it last night and for about half of the series I was like 'WTF are they even doing!?' because of certain things they changed heavily, but it paid off by the end. They played it out really well and kept the same sort of twists from the original doing new things with it so I was still able to be surprised in places.
Curious about what they'll do going forward because there are parts of the story that still need to be told, but they also completely finished the antagonist's storyline as it was in the comics so there's a weird disconnect that could be interesting going forward.
The only part I feel like they didn't do as well as they could have was the build up of the 'echo' in the well.
Overall, my biggest concern is it feels like they dumbed down a lot of the story and subplot from the original. There were a lot of really cool and complex story things going on in the background and/or past that have some heavy effects on the story that it feels like they abandoned for fear of not being able to wrap it up nicely at the end. It's hard to say though because the creators are heavily involved in the show so they may have shifted things around to throw people off. I hope so.