New, faster folder implementation
We could expound on how BTree-based folders are good for one of situation and regular folders good for another — but that would just bore you. And now it's irrelevant. Plone 4's new folder implementation means there's less to worry about. It's just simpler and faster for your users.
Did we mention that upgrading your existing folders is totally transparent and automatic? It's just one of the major gains you get effortlessly with Plone 4.
As you can see below, the results are pretty dramatic: