Is the Great Ocean Road worth it as a day trip?
The Great Ocean Road is worth it, but the one-day dash is often the weakest version. Overnight if you can; otherwise accept that the day is more road than romance.
Answer
The coast earns its reputation, but the experience changes with pacing. A one-day trip from Melbourne can work if you only want the famous cliffs and accept a long day in a vehicle. An overnight lets the road feel like a road trip: small towns, beaches, forest sections, light changing over the coast, and fewer stops reduced to a photo. The practical question is not whether the Twelve Apostles are famous enough; it is whether the drive gets enough time to be enjoyable.