I just found something that should be looked at. It seems that deleting a mailbox with this method will orphan the store resources. So...besides not only leaving the info hogging up the server's disk space, the next person to get that mailbox name will find their mailbox already populated with someone else's mail!

The M$ method uses DAPI to delete the directory object AND the store.

Reference:

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q284199