I did same about a year ago. Sold my Nikon D600, Flash, along with five high ticket lenses in favour of the FujiFilm XE2 and have not regretted the switch one bit.
Well, I cant speak for others, but I dont look into mirrorless because I want a smaller camera. I look into mirrorless because I hope for higher image quality. Thats why I'm looking for large sensors, and top notch lenses. I will probably keep my DSLR either way. Maybe even stay 100% on it, if theres nothing around to tempt me. With the A7s, though, Sony has made a very, very tempting offer. The 35mm f1.4 also looks more than only a little sweet. If they fix some more obvious issues (that butchered RAW image format, sensor based image stabilization like the A7 Mk II, and internal 4K recording), and give us more lenses on the same level (these new Bathis lenses look really sweet already), the A7s Mk II will probably my first Sony camera. Obviously not a camera for everything, though, since autofocus is not exactly uber on them.
I kept the Canon gear but purchased a $250 Canon M mirrorless with the 22mm pancake lens sweet ! Untitled by c w, on Flickr Untitled[/url] by c w, on Flickr[/IMG]
Well, even if I get a mirrorless camera (currently looking forward to Fuji making a medium format camera - I hope its a mirrorless based on the Sony 44x33mm sensor), I wouldnt get rid of my DSLR, because it will still have advantages (stamina, optical viewfinder, autofocus with sports). Also I'm planning on getting nothing but prime lenses for the mirrorless (because more light, more bokeh, more "zen" aka one less photographic variable to think about, more image quality and more compactness) and keep the DSLR for the zooms.
Oh second thought - I remember how it was when I got my D600. I first wanted to use D5100 and D600 in parallel. But quickly it turned out the image quality of the D600 was so much better I pretty much exclusively went D600. Mind you, at ISO100 and well exposed and with the sweet spot of the glas there wasnt that much of a difference, but the D600 has so much more additional leeway in less than ideal situations and the sweet spot of the glas is so much broader, too. Like the AF-S 70-200mm f4 which is simply one big sweet spot.