For anyone just joining in the discussion, I enhanced the replication
strategy so a tree-based hierarchy can be setup (useful for improving
scale-out and for sites where multiple servers may be across slow WAN
links). In addition, when updates are registered in the database, notify
events are sent to iprop slave servers so they know there are pending
updates (which reduces replication lag). The exact methodology is described
in the wiki.
The patches have already been tested with the final 1.12 production release
(they were previously tested against the 1.12 beta releases).