Journal Line Reconciliation is a new standard feature in General Ledger for R12. In fact it's not really new, in 11i it was already available as a globalization. This functionality is frequently used in Europe (not sure about the rest of the world), it gives more control for your accounts that should have a zero-balance.

Folder tools are a useful feature for displaying and sorting data in table-formatted forms. However, I experienced a lot of problems with folders in an upgraded R12 environment. Especially when custom folders are opened by default in forms, users couldn't even close the form because of the repeating error messages. Needless to say this caused some frustration.