Regarding the RX100 vs J1 question.
I have not done any rigorous comparison, but my guts feeling is:
- In terms of image quality, the RX100 is overall more detailed, DR seems to be pretty similar (slight edge in favor of the J1 perhaps). I feel that the J1 is a bit better at high ISO, but would need a detailed comparison to confirm this very intuitive impression,
- In terms of AF, the J1 is far ahead in terms of speed in low light situations and on moving subjects, but the RX100 is pretty good on static subjects except when it is very dark. The face detection capability of the J1 is superior and seems to pretty much focus all by itself when I want more often than the RX100,
- In terms of quality of exposure, the J1 seems to be overall more accurate (it is the best exposing camera I have ever seen, clearly ahead of the D800 for example), but the RX100 is still pretty good,
- In terms of lens, the RX100 distorts very heavily on the wide end, but this is well corrected in in-camera jpgs, the 10-30 of the J1 being less compact, is better corrected natively but does still need software correction anyway so we have pretty much a draw here.
So all in all, I will probably use the RX100 when compactness is key (meaning as a always carry around camera) or for landscape kind of work and the J1 otherwise (that is when my wife is not using it).
I'll look at raw image quality more in depth when DxO will be supporting the RX100.
I posted some recent RX100 images here: http://www.flickr.com/photos/bernardlanguillier/sets/72157630947824710/