Having now seen the movie, I can say that I mostly liked it. Save for one major plot change, there's nothing in it that I outright hated, some story choices were odd and some supporting cast could have done better (I'll get into it below), but Halle Bailey's performance is what made this movie for me and why I'd place it in the upper echelon of these live-action remakes. She WAS Ariel -- a perfect combination of childlike wonder, adventurous spirit, and the emotional center of the movie with those wonderfully expressive eyes of hers.
I understand they needed some story-padding when translating from animation to live-action, but some plot additions didn't really do anything other than help bloat up the running time. The whole
Triton-Ursula sibling subplot doesn't really expand the story so I don't understand the reasoning for its (re)inclusion at all. I struggle to even call it a subplot because outside of
a couple of Ursula's lines it's never even addressed or referenced by any other character, least of all Triton, nor does it forward the plot in any meaningful way. All this to say that it was cut from the original for a reason!
Amnesia spell: not only does it add nothing to the plot, in fact it actively takes away from it, and for that reason I'd say it was the most misguided and egregious one. I'm not even sure I understand how it works because no matter how much I think about it, it doesn't make sense to me.
Ariel makes a deal with Ursula but then the amnesia spell makes her forget about the crucial part of said deal, the one exact part that makes or breaks it. Like, how? Shouldn't Ariel wonder what she's doing on land in the first place then? I understand why they included it -- it's to make
changes to "Kiss the Girl" more palatable and make the interaction between Ariel and Eric less about the kissing and more about them connecting in a deeper way. However, in doing this they made things worse -- they took away Ariel's agency and took out the urgency out of the whole three days rule. And in the end Ursula still sabotages them, so again, what was the point of it?
Changing the
confrontation on the third day from a wedding to an engagement party was laughable. Another one of those changes that was obviously in response to the
wedding scene in the original but they misunderstood which wedding scene the internet was complaining about. What were they even trying to accomplish with this?
There's a sense of finality that exists with weddings that just doesn't work with an engagement (the reason why in rom-coms you never see anyone run and try to stop an engagement party). Grimsby kicking the ring away was funny as if the ring being gone would suddenly stop the engagement. It's also funny to me that the Queen and Grimsby were like, "It's so out of character for Eric to do something sudden like this" and it's an effing engagement party. Wouldn't it be even more out of character for him to request an actual wedding ceremony?
I loved most of the other story changes, or should I rather say story expansions, basically anything that further developed Ariel and Eric's personalities and relationship. I think they did a great job by giving them
common interests (exploring and collecting) and similar family dynamics. When the Queen said that Eric was taken in after a shipwreck, I was half-expecting him to be revealed a mer-man in the end 
I didn't like it on the first listen, but "For the First Time" works so much better in the context of its scene, and it does a great job showing Ariel adapting to the life on land and potentially regretting her decision
(another reason why the amnesia spell is redundant). „Wild Uncharted Waters“ also works better. "Scuttlebutt" on the other hand is still terrible and it should have been cut. References to the original fairytale were great; in fact I think this is the first time any of the remakes actually went back to the
original original source.
As I previously wrote, Bailey was the standout. Whether speaking, singing, or silent, she was charismatic and magical, and definitely made the role her own. It wasn't a lazy copy/paste job of the animated version, and both versions have retained distinctive personalities (Benson's being more energetic and bubbly, Bailey's more introspective – another callback to the fairytale), yet they're both unmistakably Ariel. I don't think this type of complementary casting/performance between animated and live-action versions has happened since the 2005
Cinderella where Lily James imbued the role with so much charm and loveliness, just like Bailey did here.
Melissa McCarthy, hoo boy... I feel like it's an unpopular opinion across this board because most of you seem to have loved her in the role, but she was... well, not exactly terrible, but not great either. When she was good, she was really good, but when she was bad it almost collapsed any scene she was in. So performance-wise, she was very uneven and at certain points I really struggled to understand her. She didn't really enunciate well and the faux-Italian/mafia-style of speaking didn't help either.
I really liked Jonah Hauer King as Eric and his chemistry with Bailey.
Supporting cast: Javier Bardem was super-wooden and dull, and gave probably the single worst performance out of anyone in the movie; Noma Dumezweni was lovely and warm as the Queen; and Art Malik made for a great Grimsby. I wasn't blown away by the animal cast, they were serviceable I guess, and the best I can say is that Awkwafina wasn't as nearly annoying as I feared she'd be.
Things lost in translation and a prime example why animation does things better: the whole "Under the Sea" sequence. It was mostly just sad listening to Sebastian naming all these different creatures and what they do and how much fun they have under the sea, and yet none of the lyrics corresponded to things shown onscreen, because photorealism

. It got more colorful and dynamic as it went along, but the whole sequence was this movie's equivalent of a tumbleweed rolling across the screen in a western's ghost town. No wonder Ariel wanted to leave.
A couple of changes from the original I quite liked and low-key wish they were in the original:
Ariel having to give up one of her scales for Ursula's spell to work, and the contract now being "in blood" rather than physical. It's more fairytale-like and we'd be spared of years of YT videos saying how Ariel could have just written a letter to Eric explaining everything.
Two things I missed the most from the original -- the lovely "Tour of the Kingdom" piece of score and Grimsby's line "If I may say, far better than any dream girl is one of flesh and blood, one warm and caring and right before your eyes". Oh well.
All in all, it could have been better, but it also could have been so much worse (looking at you
Beauty and the Beast). At the moment, on the enjoyment scale I'd rank it just below
Aladdin, but I'll probably have to give it another watch. I'll wait until it's on Disney+ though.