I've been shooting with my Olympus E-M5 since 2012. Many who know my collection of gear find it unexpected that I don't shoot with my Nikon setup, in which I have much more invest, nearly as much as my Micro Four Thirds (MFT) system.
Its DSL-ish form factor and diminutive size, most MFT cameras give many photographers pause. The sensor isn't 35mm, it isn't big, it makes little sound, and it doesn't have the backing of the biggest names in photography like Nikon or Canon. But, I found it to be so much fun to shoot with that I carry my camera with me everywhere and shoot much more because it isn't as conspicuous.
Mirrorlessons.com interviewed a photographer who's switch to the Panasonic GX7 has change his life as a photographer. His street photography has been enhanced by its small size and 20mm pancake lens (a legend in the Micro Four Thirds community) giving him freedom and stealth. It is a worthwhile read is you're curious about mirrorless and MFT cameras or thinking of using such a system.