I just watched Sanji and Zeff on the island and the desk scene at Arlong Park. Both of those moments really hooked me into the story reading the manga.
The story is seeming to do a great job mixing funny, serious, and sad moments in the right amounts to always keep you feeling something for the characters. It never stays one way for too long.
Yes, Vivi was great too. I like that after they win, there's still a good bit left of each arc where they take time to wrap things up and push the story forward. The boss fights are fun for sure, but the world building and the character development goes beyond whatever I would have ever expected for a story about a guy with rubber powers. The story feels real, even though everything is totally nuts.
Noland's story has probably been my favorite part so far. That everyone believed in their loved ones for so long despite all the bad things that happened, even with the big snake, I felt it was very powerful.
But more I keep remembering other moments like the guy that kept waiting for water in Alabasta and such. There's just so much good stuff in there!