I'm not sure how I feel about this. MegaMewTwo and MegaBlaziken look aight, and apparently Charizard has one. It sounds kinda cool honestly, but I dunno. Thoughts?
Also, lots of Digimon jokes are in order.
Update: Nintendo released a host of screens and a video showing off the "Mega Evolution." It works by making your Pokemon hold a "Mega Stone" item, and can only be used in battle. Think of it like your Pokemon is going Super Saiyan... or Digivolving... Video embedded underneath.