The dialogue was similair to the movie's for the most part. The first scene with Ursula and her eels is longer and there's a short monologue explaining that she's Triton's sister. There are a few new bits of dialogue, but nothing too different from the movie's.
The new songs...
The extended Fathoms Below/Where I belong-OK. It works for the show's opening.
The World Above-Good, but it almost felt like a watered down(no pun intended) version of Part Of Your World.
Human Stuff-Personally, I hated it. Some people might like it, but it was the show's low point for me.
I Want The Good Times Back-GREAT. It's Ursula & the eels first song, and it's where Sherie steals the show and doesn't give it back.
She's In Love-Pretty good. It had a sort of 50's girl group feeling to it, and it worked. Plus the kid playing Flounder nailed his part.
Her Voice-I liked it. Sean Palmer's high point in the show IMO.
Sweet Child-LOVED IT. A lot of people probably won't like it as much as I did, but Flotsam & Jetsam were always my favorite characters(in the movie and here), and it was great seeing them get their own song. Plus, it's a fun song but has a slightly creepy vibe to it at the same time, which perfectly suits those two.
Positoovity-Another Scuttle song. Not as grating as Human Stuff, but definitely the show's 2nd lowest point IMO.
Beyond My Wildest Dreams-It took me a little to realize it was Ariel's imagination, but the song itself is good. Not Part Of Your World good, but good.
Les Poissons(extended)-Hilarious. The reprise had the entire audience cracking up(I'm not giving it away, but it immediately brings to mind another Disney favorite...).
One Step Closer-I think I liked it in the theatre, but I don't really remember it now...So it's good but forgettable.
The Contest-It's a funny song. I'm glad they kept it short so the joke didn't wear thin.
In case it hasn't already been mentioned, there were signs up saying you could pre-order the Cast Recording, and that it's supposed to come out in the Fall sometime, which is DEFINITELY something to be excited for...
"I am the Phantom of the Opera! I'm the gayest supervillian ever! OoooOOOooooOOOoooh...Beware of my scented candles...OoooOOOooooh...Scented!"