My tiny team has been using Cloud Functions, Pub/Sub, and Apache Beam(Dataflow) to process tens of millions of daily events. I'm middle of the road on them.

Pro: - They are stupid fast to develop, deploy, and update. - Firebase tooling emulators makes local dev much easier. - Simple enough a developer can build, deploy and monitor; Cost less then hiring another person to handle devops. - Now has decent IAM restrictions - Baked in access to almost all other GCP tools.

Con: - Like any google product could be deprecated at any time. - They have poor versioning compared to App Engine or Cloud Run. No rollback, A/B, or multi-version deployments - Cold starts are slow. - Like any google product could be deprecated at any time.