Aside from the PCo Notification feature it also allows you visibility into the Secondary and Meta-data around the tag and tag values recorded in the tag based systems that you are working with. There are additional management features that PCo provides around localization support and registration into the SLD for remote monitoring of PCo agents: http://help.sap.com/saphelp_pco23/helpdata/en/f2/b1d0e885284db2baabef7eea15373e/content.htm
Hope this helps,
Sam
PS: The UDS is out of standard maintenance and should be replaced by PCo ASAP. You can open up a legacy port for the PCo Agents which will "act" like the UDS did and still allow you to leverage your Tag Query Templates.