While later patches (5.0.1, 5.0.2) introduced new features, they also introduced regressions. f4 became known as the "LTS before LTS existed"—a reliable target for shipping games.
"I remember the day f4 dropped. We had been stuck on Unity 4.6 for months because 5.0.0f1 corrupted our lighting builds every night. F4 was the first time I saw Enlighten bake an interior scene without leaking light through walls. That build saved our Kickstarter campaign." —
Yet, in the pantheon of Unity versions, f4 deserves respect. It was the foundation that allowed developers to trust Physically Based Rendering, to adopt real-time GI, and to finally move on from the hellish plugin-installation workflows of Unity 4.
There were three primary reasons for this loyalty: