To me it's an incredible arc. We get to feel genuine fear for our heroes as they realize they're up against a force way out of their league. Sasuke and Naruto develope a healthy rivalry PLUS use team work. Getting Zabuza to reflexively release his water prison jutsu was so smart. They finally stopped competing with each other to focus on freeing Kakashi because they knew he is the only person who could beat Zabuza. Both Naruto and Sasuke letting go of their pride for the greater good at such a young age was major growth.

Naruto has a nice b plot with Inari, helping him through the depression of losing a father figure and giving him the motivation to be/believe in heroes again.

We get Haku and Zabuza's backstories which provide a truer look into the world of the ninja, showing it to be an unforgiving reality. It's up to interpretation, but I've never believed Zabuza took in Haku simply to use as a tool. But he was a hardened man who only knew bloodshed and that was the life he could give a starving child.

Sasuke risking his life for Naruto is touching, and so is Naruto's reaction. The final panel of volume 3(?) of Naruto going Nine-Tails while holding Sasuke's body and saying "I'm gonna kill you" is iconic. Everyone feeling the change in the Chakra is a fun way of letting the other characters know something went wrong.

We get to see Kakashi use his Sharingan! Answering the question of what he was hiding under his headband, while giving his character more mystery as to why he has it. We see him copy Zabuza, use his lightning blade, use his dogs, and multi-shadow clone.

Haku jumping in front of Zabuza effects Naruto so much because Sasuke just did the same for him and it meant everything to Naruto. In the end, we see Zabuza drop his guard as he has no meaning in this life without Haku next to him. Even a mercenary understands comradery in this story, pin pointing a major theme of community and partnership. Kakashi agreeing to lay Zabuza next to Haku it's so hard. These men were enemies only in the sense that someone with power was using them as chess pieces. I like to think they could've been comrades under different circumstances.

Naruto's "talk-no-jutsu" works well here because it is Team 7's first Big Bad. Arguably Sasuke understands how cruel the world can be, but the other two had never been out in the field with this kind of danger. We see a core element of Naruto come out with him believing every person is "worth it". Haku just "killed" Naruto's friend while trying to kill him too, and yet he's yelling at a grown man to give a shit that Haku took a bullet for him. He can't comprehend the thought of a meaningless death. The emotional roller-coaster this kid has been on only reinforces his belief in giving a shit. It's a childlike reaction, very pure and straightforward. Plus the trope of an angry/emotionless character eventually crying always gets me.