Ah yes, I was startled by being able to be in a similar ballpark with a micro 4/3 sensor compared to my 5DIII full frame machine. There is only a slight IQ improvement from the EM5 to the EM1, the major change is in the ergonomics and IBS. I am able to pull 17 x 22 prints that show well and win awards with this relatively small sensor. Though the noise level at high ISO is obviously greater with the EM1 than the 5DIII, I am able to quash it at ISO 6400 without losing too much detail or color for my purposes, in Lightroom. The results are good enough for me to comfortably use these small and light cameras for travel, where weight is a significant factor for me.
The video output, however, is another story, just adequate, and not up to the higher quality of Panasonic micro 4/3 machines, a real shame.