Normal: Kirby really feels like 2D Kirby. Kirby feels so much like 2D Kirby that every tiny difference between the two feels glaring, and that's an accomplishment, particularly given that we've never had a true 3D Kirby game to compare with beyond Blowout Blast and Air Ride. It was difficult to aim the stars with unlocked vertical camera, so the patch helped quite a bit in that regard.
The only grievance I have with Kirby's base moveset is how puffing up interacts with momentum; or rather, how it doesn't interact with it at all. In all the Kirby games, puffing up has always functioned as a tradeoff; puffing up allows Kirby to move in any direction he wants, but at the cost of moving significantly slower in all directions. Abilities like Wing, Jet, and Beetle were all quite useful for giving Kirby the ability to move through the air with some semblance of agility.
In this mod, there's not much reason for Kirby not to puff up on every major jump, as it allows Kirby to carry his momentum even better than Tails can. The description seems to imply that Kirby is meant to be a bit worse at flying than Tails, but Kirby's much better at flying forward than Tails is, and has much finer control over his vertical movement. He 'ought to have a lower top speed while puffed up.
Fireball: Excellent ability. The mobility is quite fun to play around with, busting through walls feels very accurate to how the ability interacts with Metal Blocks in the original games, and the ability feels more natural in general now that it bounces off walls. Between Elemental Shield Monitors, environmental flames, and the fire enemies, it's one of the most common abilities in the game, and it feels deserving of that title.
The interaction with Springs feels a bit wonky; Fireball cancels out any momentum a Spring applies. It feels wonky when Fireball is used on a spring that launches Kirby in the direction he's fireballing in, but it feels even wonkier when used on a spring that launches Kirby in the opposite direction. Diagonal springs behave, unintuitively, like upward springs, and horizontal springs have to wait for Kirby to finish Burning/bounce off the wall to activate.
I think it could do with a delay between activations, too. It feels a bit too easy to spam in big open spaces like those found in Castle Eggman and Arid Canyon. The same delay Kirby experiences after hitting a wall would be enough.
Ice: Seems a bit helpless against bosses and monitors. Given that it's such a rare ability outside of Frozen Hillside, it's fine. Nice to see Canarivores give it now.
Stone: Excellent ability. Bouncing off enemies with it is hilarious. Breaking through floors is always handy. Not un-stoning on Springs was the only major grievance I had with the ability, so this update fixed everything.
I do think it has a bit too much availability, especially in Arid Canyon where both the Minuses and the Green Snappers provide it in addition to Force Shield monitors. Minuses or Green Snappers 'ought to give a different ability to give Arid Canyon a bit more variety; Needle, perhaps?
Bomb: Right where it needs to be now that it breaks walls. Feels like a proper reward for finding Armageddon Shield monitors. Perfect.
Spark: Currently the most underwhelming ability in the game, especially in the context of how common it is. To be fair, Spark was very underwhelming in Kirby's Adventure, but it wasn't anywhere near as common as it is in SRB2. It's a Monitor copy ability, but it's not remotely useful as its compatriots (Wheel, Tornado, Fireball, Stone, Bomb). It could do with some sort of buff; magnetically attracting rings while attacking, perhaps?
Needle: Perfect as it is, though the availability feels a bit lacking. It would be nice if an enemy earlier in the game gave it; the first one I'm aware of is the Unidus in Red Volcano. Pulling off bounces with it like a regular Sonic character is quite fun.
Tornado: Perfect as it is, fun to use.
Wheel: Perfect as it is, fun to use, availability is right where it should be.
Ball: Fun to use, availability feels very lacking. The only sources in the base game that give it, as far as I can tell, are Spring Shells and Bubble Shield Monitors, and that's a shame given how fun the ability is to use. It would be great to bounce through the tight corridors in Egg Rock or Deep Sea.
Sword: It's fun to slide slash through monitors and enemies. Doesn't do much for Kirby's mobility, but it's a surprisingly rare ability, so that's fine.
Hammer: Perfect as it is. I wish there was a source for it in Arid Canyon Zone Act 2, though; there's a lot of Amy paths that Kirby has trouble taking. I believe it's the only Copy Ability that can destroy spikes?
Mike: The third activation can be reused/recollected infinitely if Kirby takes a hit after the damage and gets the star back. Apart from that, it's great.
Sleep: Seemed very strange that Eggman monitors didn't give Sleep before, quite happy with how the ability is used now.
UFO: It's UFO, it feels like UFO, it's rare, it's fine. Only issue would be that it feels a bit weird for the shots to go in the direction of the camera when Kirby's air puffs go in the direction of movement.