Started playing this for the first time after missing out as a kid. Some initial thoughts:

• seems darker than BK with Bottles the Mole dying in the opening sequence, some Jinjo king guy getting blasted and turning into a zombie right after he helps you.
• I heard that Tooie is most vast, but emptier that BK and partially agree. The opening tutorial teaches you everything from the previous game, and the first world adds so much with all the different playable characters/transformations along with all the different rooms/areas to explore that it feels a little overwhelming. There's warp pad shortcuts within the worlds so that does help with backtracking.
• Controls are slightly changed. Flying seems overly sensitive, but you have options to invert Y axis and the beak Bash GWAAAH attack seems more forgiving with auto targeting. Not sure if others did this, but while PUMPUMPUMPUM running with Kazooie, I'd spam the jump button (while others find it annoying, I never get tired of Kazooie's VROOO sound). That doesn't work anymore because it switches into the flying PRWEEE jump and then you keep back flipping when you land. Minor annoyance, but now I have to wait to VROOO jump again as soon as I land instead of spamming jump.
• What seems like the hub world is pretty huge and seems kinda empty (some parts literally are that way for the story it seems). Something about it give me a bit of an OoT feel though. Maybe it's the camera animations that fly through an area like Navi does at the beginning of OoT.
• Banjo's voice is partially changed. Still the nice goofy voice when talking during dialogues, but his jump sound has a weird deep voice that does not match his character. Why'd they change this randomly?!
• Some of the cartoony charm is missing. Instead of "everything can talk", you have this weird guy (I think Bottles' brother) who appears on the screen to explain what each item you pick up is for. He also reminds me of Fi from Skyward Sword where he has to explain that everything instead of letting you explore. Leave me alone (give me back Bottles, he wasn't annoying like you)!
• Soooo much more (non-async) dialogue and cutscenes. Let me play the game and advance the story at the same time. Don't block me every few moments.
• Feels a little less like a collectathon now that most things come in batches.
• Jiggies have "objectives" that show up in the hints section so you're not clueless about what to do which is a nice touch (making it more similar to SM64, or SMO since you can do any at anytime).

I'm interested to see if I go through and finish the game. I'm still enjoying it and not too turned off by the above issues, but not sure if I'll feel like 100%'ing this like with BK.