There is so much potential in PO History, it just takes time to dig into the potential so we can advise the end user. Would be great to use this post as a forum for tricks and tips of the new tables.
One thing I have discovered is that the Purge obsolete PO utility ALSO purges the PO's from the history tables. I am trying to determine an optimal way to clean the crap out for purchases clearing from 4 years ago. I ran the purge thinking only the open table would be affected, but it also cleared the history. Probably a WAD but not what I desired. Back to the drawing board for clearing 250 PO's.