Chiaki might be the reason case 5 isn't as good as it could have been, for me. It's like Kyoko sometimes in DR1; I don't like it when the trial is kind of put on fast forward because a person's almost got it all figured out and expresses as much. It helps the tension when there's a slight bit of methodically placed confusion where the characters aren't sure what's going on, or that they're being misdirected, and I feel that frequent "You know what this means, right, Naegi/Hinata?" messed with that.
Other than that part of the trial, it was definitely the best case in the game, and potentially the entire series. The revelations were just really crazy, and Nagito was the reason for it all, as only someone like him could have pulled something like that.
It'd be really cool if the player could reach the conclusion that Nagito was actually trying to kill everyone rather than just the traitor via inference rather than just having it told to them. I'm not sure how it would be done, and I still think it was cool as is, but I think it'd be pretty crazy as a player to realize that on your own.
I think I realized that too early during the trial, so then I had to read through several lines while thinking "Morons, this obviously wasn't a suicide!" I initially thought he had put a bit of poison into each of the canisters, though, so that every single person would be a blackened.
When that building was burning earlier in the chapter, though, there's only one thing that came to my mind while they were trying to extinguish the fire: "Why?" I would have let that shit burn. Look where it got them!