We met them today! It's a Monday, park open at 10. Baymax and Hiro were due to meet and greet starting at 10:30. We got in line at 10:20, and the CM there told us to expect a 30 minute wait. It ended up being a little less than 25. Our Hiro was great! Looked just like him, very talkative with the kids, great pose for the photos. Baymax can't talk, but he can move and hug. He can't really bend his knuckles, but he will attempt a fist bump if you ask. (Hiro does a fabulous one, FTR! I think I have a little crush on him.)
ANd yes, they are having issues with Baymax staying inflated. The CM kept saying, "Baymax is a robot, and sometimes they have technical difficulties, so we can't guarantee that he'll be here." But he was out at least the whole time we were there.
(Felt a little sorry for parents arriving in Fantasyland around 12:30 and thinking they were going to get in line to meet Anna and Elsa with their daughters. Especially when the little girls were completely decked out. Must be a major disappointment.)
FInally, random, but Fireworks were cancelled tonight. We couldn't feel any wind but they claimed "winds at high altitude."