Purchased the RX-100 from DigitalRev about two weeks ago and love this little jewel as compared to my previous S95 and S100 Canons. Don't get me wrong, the S100 is still the best P&S camera out there with its feature set and ability to shoot RAW...maybe up until now.
The RX-100 is extremely fast with little shutter lag. IQ is considerably better than the S100 in most regards. The ZEISS lens is incredibly sharp and provides great color renditions. As a big fan of ZEISS lenses, this was that proverbial icing on the cake for me. (I have only recently started shooting with ZEISS ZE lenses for my Canon DSLR's)
It DOES however take a little more time to boot up and shut down than the S100 and what you don't see here is that when you turn the camera on, the lens projects about 1-1/2" before you zoom.
Additionally, the RX100 doesn't connect with EYE-FI cards whereas the S100 has a menu item for these WIFI cards. I typically use EYE-FI to automatically transfer images to my IPAD for ease of cataloging and emailing.
So, RX100 or S100? For now, I'll be using the RX more often. I'm confident the next generation S100 will out do the RX100.