The primary reason why I bought a mirrorless camera was the weight factor (X-Pro II weighs almost half of a full frame DSLR body).
So why did I sell it or better to put it, never really grew to love my X Pro-II? It was simply a matter of feeling (along with certain technical reasons).
I could not get over the lack of full frame experience and as being a person lazy to set up her tripod most of the time, the image quality of my Fuji shots were almost never comparable to the ones coming out of the Canon 5D Mark II.
Fuji felt too much like a computer to me, despite its very retro and amazing look.
For more on why I went back to DSLR - you can visit my photography and travel focused website - Bizarre Journeys.