@CCC:
^This, for sure. The other series' VAs just seemed like typical, plastic, Japanese celebrity fare who couldn't give two shits about being there (again, except Toriko's, to some extent. I liked them), but OPs' were by far the most genuine and animated. They've been together for so long… and probably will be for another 10+ years.
As for Oda's health, I think his entrance onto the stage speaks to that: everyone was looking to the back of the stage (when it was his time to appear), but a Luffy balloon-animal appeared through the smoke; not Oda! While they were distracted by that, Oda shot in through the left side of the stage, doing three somersaults in a row, and popping up, "ta-da!" style after the third, all in his suit and tie.
He was a lot quieter and more reserved than the VAs, but I think that speaks to his personality; not his health. The most interesting part is how childlike he was. He totally didn't care about the stupid gameshow-style thing that was scripted into the event, gave out the prizes however he wanted, and kept getting distracted by the whiteboard behind him (he'd be doodling on it while they were trying to get his attention). He drew Bins and made fun of Naruto a bit (the whole super-flashy-and-not-at-all-subtle ninja thing), sad-face Z (on request from Luffy's VA), and Robin speaking in Osaka-accent (request from Robin's VA, which she then voiced).
This times 100%. All those videos we see of them together, you can just FEEL that togetherness and natural flow between them outside of a studio. I mean for crying out loud 2 of them have the same last name, Yamaguchi (I know that doesn't really have to do with anything, just a random funny example of how close they are, which remind me, are Kappei and Yuriko family by any chance or them having the same last name is just coincidence?) You see them all together and it's, no kidding, like you were watching the straw hats themselves with Mayumi as their leader, Kazuya as the grunt, Akemi as the cheerful, Kappei as the goofball, Hiroaki as the ladies man, Ikue as the junior (ok not really a junior, but all Chopper-like junior, you understand), Yuriko as the mature flirt, Kazuki as the cool dude with style, and Cho as the most jovial of the bunch :).