Welcome to the club!
I think it's weird they gave Garchomp a mega form. He's already a Psuedo-Legendary.
I'm surprised they gave him one, but not Dragonite.
Tyranitar is another pseudo-legendary that got one, I'm guessing the other pseudo legendaries will get one later on (although I'm not sure how I feel about a Metagross mega evolution, since Metagross is already one of the coolest looking Pokemon, and I'm not sure how they could make it look even more awesome).