I keep seeing more and more posts of people ditching their big DSLR's for these mirrorless designs.
I recently picked up the Fuji X100s, and I have to say, the image quality is very good. It's also really fun to shoot with, light and easy to carry. I find myself grabbing it when I can't or don't want to bring a 5D III with grip and L lens with me.
While there's no question of the quality of these new cameras, it seems to me it's kind of a "bandwagon" to sell off your DSLR in some sort of statement or what not. I know if I sold my camera and lenses, I couldn't afford to get them back.
For me, I went with the Fuji X100s over a second "system" specifically because it would prevent me from getting the G.A.S. and buying a bunch of lenses and things. I have specific uses for each camera this way... flexibility and superior quality with the 5D III, and small walkaround with still great quality with a fixed lens on the X100s.
I would think that once you start adding lenses, you then need to carry a bag, even with the mirrorless. Surely the DSLR's are bigger and heavier, but once you are bringing a bag with you anyway, doesn't it start to matter less that there's a few pounds difference?
I don't know. Just spewing here. Should just shut up and go out and shoot and not worry about such things 

). The gear just gets out of my way and I just happily snap away.

