I stashed all of my Heart scales and vitamins there since I barely buy any potions of any kind. (Moomoomilk all the way.)
I found it rather useful, because I most certainly disliked the fact that hold items, random items and pokeballs went to the same bag.
So... long.. scroll... Along with the fact that "why would I have a search function in my bag? can't I just make more slots to it?"
Oh well. I hope Free Space would stay for future games.