Yeah, I'm gonna weigh in here. At first I was pretty disappointed with Mega Camerupt. Its official art just looks too cartoony for me. Its basically a cone with four hooves sticking out of the bottom (and, yes, I get the volcano reference, but it still looks weird). However, the new video has certainly softened me up towards it.
Mega Sharpedo, though, looks great. I wonder what happened to the teeth on the side of its snout, though. They show them in the official artwork, but not the video preview. Anyway, I hope they release a patch for X and Y to obtain these mega evolutions. I recently trained up a Sharpedo in my Y version and it would be awesome to have it as a mega.
Mega Gallade is also pretty sweet. I'm so glad they kept it Psychic/Fighting instead of shoving Fairy type in there (like they have with so many others). Keep Fairy/Fighting for a new Pokémon altogether, don't throw it away on a mega for an already existing one. I felt the same way about Grass/Dragon.
One more thing, though. They seriously need to release more Unova Megas. I have too much faith in Game Freak/Pokémon to believe that they would only have ONE Pokémon from the Unova region mega evolve, let alone have that one Pokémon be Audino of all things.
Plus, Hoenn Pokémon already had a lion's share of the megas that were introduced in X and Y, and they've already introduced enough new ones for ORAS. Time to bring in some other regions' Pokémon. I'm hoping for Mega Beartic, Mega Swanna, and, just to piss some people off, Mega Garbodor. Plus, Mega Johto Starters, please!!