Nokia talks about "reinventing zoom." Even as the Lumia squeezes all those pixels into a 5MP image, it retains the full version for you to crop and blow up later. One nice touch: Even if you use the camera's digital zoom to focus in on a subject, it still retains the rest of what the camera sees. Other cameras throw out that data. So your 5MP version will focus in on what you want to quickly share, but you can go back to the larger version to discover something you might have missed in the surrounding area.
But digital zoom is digital zoom and won't replace what a real zoom lens can do. Among the three phones, only with the Galaxy S4 zoom was I able to make out faces of band members at a recent concert in New York.