Great write-up.
Even though the Zabuza/Haku arc wasn't a favorite of mine (it had it's good parts, but that's not the point here) it's very much true that we could've used more arcs like that before the Chuunin exam. Seen more of their training or something. The teamwork they showed in the second part of the Chuunin exam was acutally quite awesome. It also showed us that they had gotten to know each other quite well, with Sasuke figuring fake Narutos out and such. At this point Sasuke was my favorite character because he was the smart one when it came to thinking between the lines, if you know what I mean, and it really helped building the teamwork they had more than anything else. We saw this in pretty much every teamwork mission or challenge they had. If that had been going on for longer then no doubt Sasuke leaving would've been a way bigger thing than it already was. He as absent a lot starting the last part of the chuunin exam and until Naruto finally met up with him in the retrieval arc, so besides making the fact that they were best friends / like brother seem like less, it also meant that by this time I serveral characters had surpassed Sasuke as my favorites, since the times before wasn't enough, and thus made it less tragic than intended.
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Nio-chan and Ctes: http://img.imgcake.com/nio/Untitledpngyn.png
BroAndCharAndCtes: http://i.imgur.com/oBQfY.png