Hi David. Sounds like you're looking for more justifications for GAS. Well, you've certainly come to the right place!
My Dad has a RX100 and I have the new GR. In terms of handling, feel, ergonomics and ease of use, the GR is light years ahead. It sits very well in the hand and is very grippy, unlike the soap-bar-slippery RX100.
Focus is just as fast and perhaps faster with the GR in good light, but slower and more 'hunty' in lower light. The RX100 does have the surprising benefit of face detection, which I always snubbed until I experienced it with the Oly OM-D.
Shutter sound: I have a range of cameras including the X10, X100, Ricoh GXR and many others. The GR is louder than the X10 and X100, which disappointed me. It is a definite mechanical 'click-click' and audible in quiet places, but not on the street or a busy restaurant. It is also louder than the RX100, although not too much. But lens extension sound is minimal, and focusing is practically silent.
The GR's 35mm function is a crop of the original 16mp image, down to 10mp. Image quality is still excellent, as it is identical to the centre crop of the original.
It has been suggested that Ricoh believes the sweet spot of the GR lens to be f4, which is why P mode preferentially selects it 80% of the time, regardless of lighting conditions. Even at night, I can't get P mode to select f2.8 instead of f4. I work around this by shooting in P in bright sunlight and Av at f2.8 when indoors or in anything less than bright sunlight.
I never thought that a lack of stabilization would bother me, but I've been spoiled by the EM-5. The GR seems to select lower shutter speeds in low light situations, rather than increase ISO too quickly. I have tried to work around this by setting Auto-ISO to 1/125 and ISO 6400, but it still shoots at 1/80 and ISO 3200 in moderately dull indoor conditions. Kind of odd.
Apart from these quirks, I find the GR an immensely enjoyable camera. It is very fast to operate, out of the pocket, shooting and back in the pocket before anyone notices. The image quality is somewhere between the GXR M-mount module and the Leica M9, and the LCD screen is super. Just make sure you put a protector on the screen, as it appears to be coated and collects dust and fingerprints like blazes.
If you've got any more questions, just fire away. GAS Enablers Inc. is here to help. 😀