When I look at the node page (/opennms/elements/node.jsp) for a node, one thing that would be nice to see is a section which shows which services are also being used as collectors.

When I look at the service page (/opennms/element/service.jsp) for a node+interface+service, it would be nice to see information there that lets me know the service is associated with a collector.

As an example of sorts, if you look at a nodes interface page (/opennms/element/interface.jsp) in the General table on the left, it shows the list of polling packages the service is a part of, and the status of the last poll.