1. Dependency resolution algorithm failed in places that Poetry handles fine.
2. When Airflow added a dependency choice (based on licences) the setup script required an ENV var choosing one to be set, pipenv swallowed the stdout output and dumped a Pip stacktrace that didn't help diagnose the issue.
3. Mysterious bugs on new pipenv releases that usually manifested as a Pip stack-trace or setuptools stack-trace.
4. Sometimes the bugs were installed Pip version dependent, which made replication hard.
There was other stuff, but can't quite remember off the top of my head.
But yeah, we spent a lot of time trying to figure out why pipenv had broken again. Poetry has been a breeze in comparison.