This is a very minor wish compared to some of the excellent suggestions I've seen here but it needs to be voiced anyway.

The "EQUALS?" and the "NOT EQUAL?" nodes (and all the greater_than/less_than stuff too) have a comparison mode associated with them. You can either compare elements (the default) or compare aggregates.

If I have an "EQUALS?" node setup to "compare aggregates" and then decide to replace it (Rt-Click/REPLACE) with a "NOT EQUAL?" node, the "NOT EQUAL?" node should really be put in place with the same "compare aggregates" mode enabled.