honestly I don't think it matters whether you release them now or in March. I think schools generally overaccept off the bat knowing that a certain number will withdraw. Thus, if you were to turn down a spot now, its not like they'd go ahead and give it to someone else right away. Obviously you should never hold a spot at a place you won't go, but the more important thing to help out everyone else is WITHDRAWING CURRENT APPS. This really will make a difference as it will free up the committee to offer spots to people that really want to go there.
So . . . if you're accepted to a school you are dead set on going to, or if you know that there's no way in hell you'd go to a school that you have an active app at you should withdraw. I just hate the d-bags who keep active apps just to see how many schools they can get into. It's not fair to cause more waiting and agony to others just to stroke your ego.