First, thanks to Michael for giving us the perspective of a photographer who is serious about image quality, but pragmatic rather than perfectionist, on where a high end pocketable digital camera might fit into a photographic enthusiast's life.
The combination of favorable comments on A3 prints and less favorable comments on high ISO noise levels due to small pixel size makes me admire Canon's idea with the G3 of keeping the pixels a bit "bigger but fewer" (4MP instead of 5MP, same sensor size as the S50). I wish someone would compare those two models, but I know it is well out of Michael's main territory.
On aperture ratios and the S50's program mode staying at f/2.8 as much as possible: my understanding is that f/2.8 is equivalent to a 35mm camera at f/11 or a bit smaller in terms of both depth of field and diffraction effects, (and f/8 is equivalent to about f/32) so the program mode's choice and the f/8 limit both seem reasonable: with such small sensors, the aperture setting is mostly a light level controller, not a DOF adjustment. I often have my digicam's aperture priority mode at f/2.8 for that reason. (Other reviewers have criticised digicam program modes for favoring large aperture ratios and high shutter speeds, apparently without accounting for this sensor size effect.)