As I believe Ray pointed out, the ISO inflation is less than a stop -- and that's pretty much born out by others. Olympus does it also. Certainly the Fuji's are better than anything micro four thirds I've used though I've not used any other contemporary APS-C cams my last ones being Nikon D7000 and early Sony NEX cameras.
FWIW (and I don't think that's a whole lot!), my observations about Fuji ISO inflation were purely my observations, without a bit of scientific backup. I had them at just about exactly a stop, and that was relative to the Ricoh GXR, the OMD, the Nikon A, and the RX1, all of which exposed identically in my highly informal "tests". I didn't test the metering or quantify that each exposure was identical, but I found that the Ricoh, Olympus, Nikon, and RX1 all exposed the same low light scenes identically at the same ISO and same aperture. The focal lengths equivalencies were all consistent between the Ricoh, Nikon, and OMD (back when I had a Pany 14) and between the OMD and the RX1 (with the Oly 17 f1.8). I tested both the X-Pro 1 at 28mm equivalent and the X100s at 35mm equivalent. And the X-Pro consistently exposed a full stop more at any given combination of aperture and ISO and the X100s exposed more than a full stop more. So, if Olympus is doing it too, I wasn't finding that relative to this limited set of cameras/bodies... I think Gary and one or two other folks chimed in with similar findings with some Canon and Nikon DSLR gear, but I forget the specifics.
Ricoh and Amin and others got into the weeds of the testing and the science and basically concluded that it was less than a full stop, maybe as little as 1/3 of a stop, which I wouldn't find significant. But the full stop I was experiencing/observing would be. Part of the discussion was that Fuji tends to over-expose relative to the others, which would negate or partially negate the ISO differences. And I can't refute that, but it hasn't been my experience, at least to a significant degree.
So, anyway, just to be clear, I don't know how much ISO inflation there is. I also didn't find much quantifiable difference between Fuji X-Trans and the OMD era m43 sensors (low light and DR being very very close), although I see a notable qualitative difference between the two. I like both and wouldn't rank one above the other, but I certainly understand how others might. The bottom line is that ALL of these sensors are so stinking good right now, we may as well not argue over nits and just go with what we like, for whatever reason. This excludes full frame, BTW - the RX1 continues to blow my mind in ways that nothing else I've used does, but among all of the current APS and m43 sensors, I'm not seeing enough difference to obsess over...
-Ray