I was a fairly long time Sony user. I bought the NEX-6 new, preordered the a6000 when announced, and used the a6000 up until about the time the a6300 was released. At that time, I sold all my Sony lenses and flashes, and bodies and made the leap to Fuji.
For me there were several factors, none of which might be decisive in and of themselves, but taken together added up to a decision:
1) Form factor, build, and ergonomics - I liked the NEX-6 a bit better than my a6000. The NEX-6 had more of a premium look and feel that was lacking in the black bar of soap that is the a6000. The a6000 might have had better performance, but was a bit of a let down in some ways. In both cases, I didn't care for Sony menus and really craved more physical controls. I had high hopes that Sony would borrow just a bit of the design and controls from their A7x line for the next APS-C release, but instead we just got another, slightly upgraded, a6000 with a little more metal and 4K video. However, in terms of form factor and ergonomics, you can't hardly tell the a6300 from the a6000; they're both black bars of soap. I suspect the a6300 was supposed to be out a long time ago, but heat issues and other bugs delayed it. At any rate, it's not much of an upgrade, in my mind, and made me feel like the Sony APS-C camera bodies are just as stagnant as their APS-C lens line is.
2) Speaking of lenses - Acutally, I wasn't that bothered by the fact that Sony hasn't released an APS-C lens in years. I had a bunch of them and felt like I was pretty well covered. It's just that they weren't that great. Sony APS-C lenses are either a) mediocre, b) overpriced, or c) both at the same time. Some are okay, but few if any are great.
3) Directly related to #1 and #2 above, regardless of what anyone on the Sony forum says, I really do believe that Sony is pretty much done with any serious R&D on APS-C systems. Oh, they might put out a new body here and there to keep a few entry level dollars coming in, but make no mistake, they are no longer particularly interested in APS-C. I'm not that interested in going FF so I tend to think my interests are going different places than Sony's interests are. So, probably time to part ways.
4) Cameras vs. Gadgets - This one is perhaps the most subjective and hard to define, but I always felt like Sony cameras were packed full of gee-whiz technology but were painfully short on input from long standing working photographers. As an old film photographer (though not professional) Sony cameras always felt like high-tech gadgets, but never quite like serious cameras.
5) LOVE - Okay, I was wrong. This one is the most subjective by far. I just never loved my Sony gear in the way that I do my Fuji gear. I am truly addicted to holding, using, and thinking about Fuji gear in a way that I never was with Sony. Fuji has captured my imagination again after many years and rekindled my love for photography. I can't imagine ever going back to equipment with no soul.
