We changed "rename" to "rename_it" (kinda dumb, but thought "ren" would be more confusing). All default values have to match between header and bodies of packages, about a dozen of which slipped by unnoticed with 8i. And the relational constraint checking views rel_constraints_violated_one and rel_constraints_violated_two produce the infamous and dreaded "ORA-03113 end-of-file on communication channel", so we changed them. I don't know as they ever did us any good before, so we can't tell whether our altered versions are any worse. There was one call to ctx_doc.filter which was getting confused picking which version to call. All in all, I think most of the "problems" are actually Oracle 9i being stricter about enforcing things that probably shouldn't have happened in the first place.
