Had another thought on this topic. I was watching a photographer a bit ago taking pictures of a balloon race. The guy had the best of equipment, but it was all the latest Nikon stuff -- very heavy. He kept looking at me and my Fuji X-Pro1 -- a mirrorless "gizmo" that harkens back to the Leica that once was -- little small cameras that just worked.
We probably got very similar shots, but when I got home, my back didn't hurt.