The ability to search for a piece of text across the entire IDF (Models, components, include procs, global procs etc.), and either be able to do search and replace, or click to be taken to the correct place in the proc (The ACTUAL line the search string was found on) to allow for easy mass changes.
Too many to list.
Makes ongoing maintenance of a complex system much faster, allows for multi developer updates (which current technique of dump to XML, change and reload doesn\'t).
Uniface Development Environment