As stated earlier, Gula was kinda a very big letdown. Sky already explained how the scale was totally reversed, but I think it is worthy to note that Black Knights' behavior in general is rather more on their conviction and "mission" so to speak.
They rarely waste their time with arrogance and the like, so seeing Gula and Ira going "fufufu" was rather a bad surprise.
As mentioned already before, taking down the Black Knights required a lot of teamwork and some sort of luck:
Gula, for instance, had to be kept at bay with Kukuri's chains (who joined before Yukiko and Takahisa), and Misuzu was forced to keep Kashagiri, the flame sword (By the way, Misuzu had to deflect or dodge Gula's attacks. In the anime, she could parry, which is ridiculous: if it was the same scale in the VN, Misuzu would have been a petty stain on the ground, squished like a tomato).
Even with the struggle, they could barely contain Gula "normal" swings and his "splash damage" due to the crumble he generate by crushing the gound etc. Yukiko barged, surprising everyone, but "died", then pretty much like in the anime, caught Gula by surprise, throwing a knife (which is normal, since he didn't expect her to be alive anyway). But that's only the start, as she had to harass him, focusing on the wound and acting as a cannon fodder (she took countless damage, but kept harassing Gula's weakness). In the end, Misuzu could cast Kashagiri's spell and cleave Gula, only because Yukiko multiplied the number of lethal attacks on Gula, buying her some time (Misuzu was casting Kashagiri's chant, taking an awful time + a 3 hit slow skill that had to connect).
Meanwhile, Ira's death was really too early and stupid at best. Should he were to have the same opportunity in the game, he would have killed Kakeru right on the spot, instead of grabbing him and toss him just for fun. (He is wrath after all, not like he cares about toying with them: he is probably the most zealous in his mission, unlike Acedia). For your instance, Ira was supposed to be gouged in the eye, as Kakeru managed to dodge him by "chance" thanks to the eye, then took this chance to stab Ira, with human means, not with a sudden ridiculous somersault).
I personally fear a lot for Superbia, considering how they introduced her with her quick clash with Misuzu (which shouldn't have happened to begin with)
The problem was kinda worsened with a plain animation (design was fine, but the movements were kinda plain, and actually: I wasn't having any "speed impression" when Yukiko was assaulting Ira).
Now, my biggest gripe lies elsewhere though: the characters. Although Kakeru and Yuka didn't change negatively, the rest did I think. Oh wait, there is a major problem with Kakeru: how his "growth" is disproportional. You see, Kakeru was pretty much forced to train a lot with Misuzu, with training shinai (no real sword). It wasn't as sudden as seeing him with a real steel katana, swinging a candle (Any amateur would have grand chance to hurt themselves, or at least getting tired after only few swings).
But what astonished me the most is the fact Kakeru didn't need any "attunement" in order to wield Raikiri. Like Misuzu mentioned in the anime, she inherited them, hence she is the swords' master. Should anyone dare to pick them up, they would simply be engulfed by the sword power, as a "protection". Kakeru basically payed the priced when he tried to pick up Raikiri once in an urgent situation: he was almost killed by the electrocution. In fact, Kakeru had to "tune" himself with Misuzu's blood (she actually cut her finger a bit, and they start some sort of ritual on several occasions, which drains a LOT of Kakeru's stamina).
Misuzu is more "kuu" than "dere", which is hard to brand her as a "companion", as it seems she is just doing all this stuff out by duty instead of consideration (that might be my impression, but she looks much less friendly... or it is because we don't have the same antics?).
Regarding her skills, nothing really changed, but it is hard to figure the usefulness of having 5 swords, if she is using them without much afterthough or spells.
Just for your information, each sword has a specific specialty: Raikiri has, of course, a lightning ailment, with a splash/AOE effectiveness; Kogarasu is used for swift and nimble strikes; Kashagiri is for brute strength, coupled with a fire ailment; Kanagiri is for defense purpose along with range modulation. Finally, Yasutsuna has something different, but better not to spoil now (though it appearance and aura should be a big hint already).
I would say they basically trivialized her skills: without an actual weakness (no LONG chant to summon the swords) or define style (she is using Raikiri and Kogarasu almost the same way), she seems to use some kind of lightsabers of different colors, randomly. Oh yes, I still wonder why they made her dual wield Kogarasu and Raikiri: not only it doesn't help her, but dual wielding Katana is anything but cool or effective: it is reducing your effective range by a lot, draining much more your stamina due to the uneven weight on both arms, and a very bad accuracy to boot. So her with both Kogarasu and Raikiri not only make them like mere weapons, but Misuzu is actually looking like a wannabee samurai.
Yukiko antic mode seems to have skyrocketed quite a bit: because of that, it is kinda difficult to have a tragic impression (well, she is too much like Ciel from Tsukihime).
Kukuri's introduction was totally belated: she is the first person to join Kakeru, Yuka and Misuzu, and actually, without her, they would have almost 0 chance to survive (her chains and abraxas' powers). and I still don't get why she put these cryptics message, even with my game knowledge.
But the biggest change was prolly Takahisa: he is plain annoying and apathic at best, which is the complete opposite way to begin with! He is the kind of lecherous and merry buddy of the group, often starting antics with Yukiko, much to Misuzu dismay. And no, he doesn't have anything against Kakeru at all.
For those who are curious
Spoiler for game: Takahisa's first appearance before Kakeru and Yuka:
Kakeru and Yuka were shopping a bit, but Kakeru bumped on some punks, who started to pick a fight with him. They start getting excited as they see Yuka, but of course, Kakeru gets in the way, and get his ass kicked.
As he is about to be beaten to death, Takahisa shows up with his trademark KFC cup.
The delinquents know him and they are annoyed to see him again in their way, so they are threatening him. Takahisa doesn't take them seriously, joke around though he isn't exactly enjoying to see them bullying Kakeru and Yuka.
Takahisa has no problem to take care of them, though one of them pulls a knife. Takahisa manages to own him, and the assaulter gets cut himself with the knife. At that point, Takahisa really goes in a "yakuza mode", scaring the shit out of the punks, who run away like no tomorrow;
After the commossion is dealt with, Takahisa gives a hand to Kakeru to stand up, nicknaming him Romeo. He isn't belittling him one bit and cheers him up.
Funnily enough, he was the one who made his way to the club, without anyone knowing that he was also caught in the red night. Because of his pervert comments etc, it wasn't exactly much to Misuzu's liking, nor it was convenient for them if they wanted to talk some preparations against the black knights.
Basically, he has a 180° switch in the anime, and not in a good way if you ask me.
Funnily enough, not only they put unecessary foreshadowing (like the Black Knights comments regarding Kakeru's eye or Kukuri's weird sketch), but the scripters omitted proper foreshadowing (Vlad's memories, except one).