The G16 shows extremely subtle improvements over the G15 -- but you really have to scrutinize to see that there's slightly less detail degradation (I think the exposure difference is from slightly different angles during the tests, which were a year apart). The Sony Cyber-shot DSC-RX100, while not perfect, is still better, in part because the higher resolution provides better preservation of detail.
ISO 400 is the highest I'd recommend shooting with the G16, since this is the top of the range where it can still deliver sharp, well-resolved textures.
(1/80 sec, f2, evaulative metering, AWB, ISO 400, 34mm)
Photos at ISO 1600 don't look very good displayed at 100 percent or printed at large sizes (13 x19). They look fine scaled down by about 50 percent or so.
(1/60 sec, f2.2, spot metering, AWB, ISO 1600, 56.5mm)
Canon pushes the saturation so that reds get a little too glowy, but that's pretty typical. Generally, the colors are pleasing. Disappointingly, though, you can't use the neutral color profile when shooting raw or raw+JPEG.