I would agree with liam about rangefinder adjustments. It's a non issue.
I'm really confused by the RX-1, though. No viewfinder, only contrast detect AF, fixed lens, fairly large size, and over $2,500. I get that a FF sensor adds a huge amount of cost and some size. But if I'm spending that much cash, I want a viewfinder, even if it's electronic. I also want phase detect AF for moving objects. And, though I can happily live with only a 35mm lens on FF, I want at least the ability to change lenses. It seems to me that someone would have to be a fairly serious photographer to be willing to spend $2.5K and I'm not sure one would want to make so many compromises. And, to add insult to injury, the camera isn't that small. It's not pocketable. In fact, it's a bit weird how large the lens is given how small an equivalent 35mm Summicron is.
I'm going to sell my 5D2 in a couple months and get a 5D3. With its AF system, that could be the last DSLR I ever own (or, until it breaks). I never had the same feeling about my 5D2 but it was the tipping point where I felt DSLRs were mature enough that I could take the plunge. I still don't think mirrorless cameras have gotten to the same point. I would want at least an APS-C sensor, relatively small package, some sort of viewfinder even if only electronic, and a good collection of native lenses. Contrast detect AF is OK; the OM-D is a great example of how good it can be but the m4/3 sensor is just too small. The Sony NEX 6 is almost perfect but the e-mount lenses aren't quite ready yet, I think, in terms of quality and selection. And it's also odd how large the e-mount lenses are. I'm not an expert in optics but I would have thought the relatively small sensor and short register distance would have allowed for smaller lenses.
As to the new 35mm EF lenss, that new Sigma looks pretty darn good. But I already have the 35L so it's not something I would buy. I did have the f/2 IS Canon on pre-order but an interesting gun came available for sale so my fun money was diverted. I'm going to read some of the reviews and place another order based on those. I do still have my old 35/2 and I don't think I could ever sell it. It so small and handy and I've had it for years, long enough that no one would give me enough to make the sale worthwhile. Lately, I've cut down on my travel set to a 17-40/4L, 35/2, and 100L macro. Replacing the 35/2 with the IS version would be pretty unbeatable in low light situations when shutter speed doesn't matter.
Edited by leftnose - 12/4/12 at 10:44am