Was that girly? Well, whatever, I guess ┐(´・ω・`)┌ And yeah, I'll order one soon -- as for the game itself, probably I'm getting Y after all. Sis wanted X but unless she still persists (as I mentioned she doesn't hold much interest as she did when Gen VI was first announced) I don't think it's wise to buy both right away on release day...
As for mega evolution, I think you need to do it every time your Pokemon enters the field of battle. In my view, it's sort of like stat-enhancing buffs and similar set-ups (Aqua Ring, Leech Seed, etc) that disappear when the Pokemon is switched out or abilities that reactivate when the Pokemon is switched out and back in (Intimidate, Slow Start, etc).
...Probably the only way to make it worth it is to NEVER switch out at all.
Quick, start a petition to Nintendo to ban Roar, Whirlwind, Dragon Tail and the like!