The G series bodies are rather large and bulky, unlike the S100 which I can wear on my belt. So I believe this guy is a competitor to the S100.
However, as much as I like the idea of large sensor small cameras (and may be buying one), I'm not sure I get the point. They'll never be as good as the DSLR, and the DLSRs will never be as small and lightweight as a pocket cam.
I love my S100 for the small file size, good enough shots, GPS, quick and easy movies, metal body and ease of use. Would I pay twice as much for twice the sensor size? Not sure.
I think you need to take a look at the images comming from the G1X because they're every bit as good as a DSLR. In fact I hear people saying the images are better than the Nikon D700 & D3 with the 24 - 70mm f/2.8 and that's from two different sources.
Then there's the statement from Canon that their new compacts will have 'similar' image quality.
Large sensor compacts might not yet be as small as a true compact, but they're a fantastic development. Take a look at the 'is the DSLR becomming an endagered species' thread to see what other people think, and some amazing images taken on mirrorless cameras.