The Toy Story world was kind of small and simple though I did like the pacing of it from a gameplay POV. I wasn't keen on the toy robot gimmick from the trailers, but those sections ended up being pretty fun (I think it helped that the pilot-able robots do absurd amounts of damage, like they don't seem to have been rebalanced for Proud at all... not that I'm complaining). The Tangled world seemed really cool with the size of its maps, but I was really strained for time so I ended up rushing past most of the encounters. I don't have much else to say, as the bosses haven't really wowed me so far (and that's actually kinda disappointing).
I guess the Mother Gothel fight was challenging, though that was partly due to the lack of checkpoints, some janky aspects to the boss (like that headbutt attack, dear god that attack can be absolute BS sometimes) and that crappy gimmicky flowmotion section (it's not too hard but you can get really unlucky with some bomb spawns). I also want to mention that the Flower phase later in the fight is pure *evil*. Like shit, I'm not sure you can even escape if you get caught on Proud; I tried everything but the only thing that worked was fully healing myself so I could just tank the hit.
As for the combat so far: I think I really, really do love the new changes. It took me a while to figure out that the powered up forms are kinda like the command styles from BBS, and when I did it all kinda clicked for me. Having that system from BBS but with so much more control over when to activate the style change by itself was cool to see, but then learning that you could keep powered up keyblades / different command styles in reserve via the Keyblade switching mechanic was just amazing to discover. That was a really inspired decision and it's really opened up the combat for me. There are all sorts of other smaller changes that I really love (the new Blizzard spell letting you ice skate is cool af, and the KH2 style team up attacks will revive KO'd party members so no need to worry about them being alive), though the keyblade switching is probably my favorite mechanic.
So far I've been running the Kingdom key (sometimes I need a key to use while the other two keys are powered up and in reserve, and this is a better option than the Arrowgun key which seems to be way too weak on Proud), the Toy Story key (it's got the best damage so far and the drill form is also super good for faster travelling) and the Hercules key (this thing is my run's MVP; its shotlock heals you, it's guard makes you really safe, it's counter is one of the only ways to get decent damage on Proud, and even its random finisher is good for stalling when you need MP to regenerate).
The combat system still has its issues for me (the floatiness still sucks and I've had a few stupid deaths because I couldn't fall to the ground fast enough and just kept getting hit / bounced back up;, the flowmotion can be finnicky to control during the heat of battle, especially when fighting aerial bosses where the camera kind goes nuts; I'm not a fan of Links / Summons being tied to MP and requiring all MP to be usable) but I'm definitely loving playing through this game, the damage spongey-ness of this Proud difficulty aside.