I lost it at Gui trying to describe his special sound effects.
Also, I'd like to say now that the supposed drawback to having your pokemon be a mega evolution is the loss of their hold item slot to the Mega stone they have to hold. this of course keeps you from being able to use Life Orb or choice specs/scarf/band for their raw stat multipliers.
Mega Garchomp actually gets a speed reduction that he trades out for sheer defensive bulk and offensive prowess.
moreover, I have come to the conclusion that I like and dislike Mega Evolution. on the one hand, it takes pokemon that were TERRIBLE (Charizard, Mawile, Bedrill, Pidgeot) and gives them chances to shine or gives pokemon a completley new strategy to work with.
On the other hand, Mega Evolution is literally the fanservice button. Charizard and Mewtwo are probably the two most popular pokemon outside of like... Pikachu and maybe Eevee? notice that they get TWO mega evolutions? notice that most mega evolutions are of generation 1 Pokemon instead of the newer stuff? (Audino is the only Gen 5 mega to my recollection...)
Also, this mechanic breaks anything that was battle tower ruleset based, such as battle spot, the pokemon national championships, ETC. These things often have better BSTs than most legendary pokemon that are outright banned from these, and in the case of some, they have better abilities and movepools than those 'banned' legendaries.
On top of that, OR/AS outright BREAKS the mechanic altogether by having made Mega Rayquaza, a Pokemon that is so stupidly strong that it can defeat the most powerful defenders in the game with a single hit of life-orb boosted Dragon Ascent (the new exclusive move that is Rayquaza's supposed 'price' for mega evolution... which let me add is the flying type equivalent to Close Combat... y'know, the best fighting type move in the game.)
Still, it's fun hearing TYP catch up on 4 generations of tweaks to the gameplay in one fell swoop all the same...!