Yeah the immediate reaction is to cringe whenever there is something written that could at all be interpeted as *negative*. Still, they have to write something in the weakness section and simply saying that you're "detailed oriented" as pseudo-weakness won't fly.
This is actually a very legitimate and relatively *safe* weakness, as weaknesses go. As you alluded, this is a key reason for you wanting to get you're MBA and something that you will learn from in b-school (especially given the great schools you're targeting). So, I'd say it's fine -- just play up the fact that this is something on which you're actively working and that you want to continue to develop at b-school elsewhere in your application.