I've had a Sony NEX-5 and now a Sony NEX-7 for a couple of years now.. I love the smaller format and quality is every bit as good as any APS-C level SLR.. I bring it virtually everywhere all the time and people hardly notice or care that you have it...
I have been collecting a decent amount of really good classic glass for my Sony as well because of the shorter flange distance I can even buy small Leica rangefinder glass amoung others and just adapt it for use..
I chose the sony over micro 4/3 competitors because of it's APS-C sensor (only a 1.5 crop), superior EVF, highest resolution tiltable preview screen, focus peaking and very small size..