Interesting question. I flew my first airplane five years, many trips, many hours IMC & IFR with an Escort 110, KX145, and marker receiver. No xpdr, no intercom, no audio panel, no weather display, no moving map, no autopilot. I thought I had it made because I had TWO radios! The aircraft I trained in had only one VOR, one comm. Lots of people routinely did the same. Up to the mid-50s people did it Pt91 without gyro horizons & gyro compasses. Is the fact that people seriously ask this no-autopilot question the reason why the FAA is putting emphasis on evaluating the hand-flying skill of aviators flying aircraft which have autopilot installed? Hmmmm..............progress!