You wouldn't know it from all of my jumping around, my tour around the camera world over the past couple of years has actually confirmed how happy I am with the current state of affairs. The ONLY advance that will likely make much difference to me (and maybe only me) going forward (other than continuing inevitable improvements in sensors of all sizes) is whether really good fast full frame lenses can be scaled down to about the size of APS lenses currently. I think almost every new camera of reasonable size (I don't like 'em too tiny or too big) is at the point of being excellent in terms of interface and performance. This wasn't the case 3-4 years ago but it is now.
I think shooting with a DSLR for the past month or so has confirmed for me that I like 'em well enough but I really prefer a good mirrorless live view / EVF setup than a great OVF with a barely useable live view. And I'd imagine that full frame sensors will always be more capable than APS or m43 sensors. But I can't imagine I'm ever going to be willing to shoot with fast full frame lenses at the scale they exist today, particularly at the longer and wider focal lengths than the 50mm neighborhood (where they've been making good fast ones at a reasonable size for many years). Which means for my purposes, there's not all that much difference between full frame and APS by the time you compare the slower full frame lenses I'm willing to use against the faster APS lenses with a "slower" sensor.
I might be willing to go with somewhat larger lenses with a small mirrorless body than I am with a full frame DSLR body - I'm OK with the size of the Df, but only combined with smaller lenses, even their faster 28 and 35mm primes are getting past my tolerance, let alone their really wide and long lenses. We'll see as the full frame mirrorless thing continues to mature or not with the A7 / A7r and any competitors it may spawn. For now, though, I'd love to shoot with full frame but not with the lenses I'd have to use to gain a real meaningful advantage over APS. So I'm gonna stick with APS and m43 and keep my eye on mirrorless full frame developments. I have my doubts about what's possible but I maintain some amount of optimism due to the really small APS primes Pentax has managed to develop for it's APS DSLRs. They're not all that fast, but they do seem to have defied the laws of physics to some degree so maybe Sony or someone else can do the same with full frame mirrorless?
If that one can be solved, I'll probably jump to some full frame system at some point. If not, I'm happy enough with current APS and m43 offerings and will be happier yet as the sensors continue to advance. But short of smaller full frame system components going forward, my past year with the RX1 and month with the Df may have just been a really interesting experiment. I loved the RX1 with it's 35mm f2.0 lens, and if I don't like the APS Fuji with the 23mm f1.4 as much, maybe I'll buy some similar fixed lens full frame camera going forward, depending on what they may come out with. But if I like the results with the Fuji as much at 3200 as the RX1 at 6400 (which I'm sure will be close enough), I'm probably staying with the crop sensors until some miracle of full frame lens sizing happens...
-Ray
I understand your reasoning and can`t disagree with it. Except, maybe, that there is a small number of cameras out there, whith something more up their sleeves than just the sum of specs. The RX1 and DPMerrills are in that small group and maybe the Df. The X-T1 with the 23mm, at least on paper, should match the low light capabilities of the RX1 and its slower lens. However, I doubt that the technically competent Fuji lens draws as magically as the f2.0 Sonnar coupled with the Sony FF sensor does. You mention your tour around the camera world over the past couple of yours. Trust me, my closet, and unfortunately the bank account, have seen too many cameras and lenses come and go in the last few years. The good thing is that technology has know reached a level which should allow to fight back on GAS and focus more on photography.