and, if you think about it, it actually makes your battling pokemon gain more stats than it normally would at level-up. it gets the same EVs, but only half the exp. so by the time it's hit the next level, it's gotten twice as many EVs, and therefore gets more stats. ... of course, if its EVs are already maxed out, it has no effect.
EXP SHARE / RARE CANDIES DON'T MAKE YOUR POGEYS WEAKER! why do people always think that?