2 Years.....The Difference IS Different.Differences between a couple of years for canon....after work I had my two canons with me, I said I have 15 extra minutes. So I stopped down to the fairly well lighted town square around 9pm.
Canon SD800 7MP ($390-2007)
SD800 sensor= 1/2.5" CCD
Canon S90 10MP ($425-2009)
S90 sensor= 1/1.7" CCD (larger of the two sensors by about 70%)
My images below: SD800 left side / S90 right side. Both ISO 800. Auto Settings. Only composited and resized in Photoshop.
cartop (self time on top of car) > f2.8, 1/3sec | f2.0, 1/6sec

Below are all handheld....
arches > f2.8, 1/20sec | f2.0, 1/30sec

wide arches > f2.8, 1/10sec | f2.0, 1/20sec

fountain > f2.8, 1/15sec | f2.0, 1/30sec

palms > f2.8, 1/13sec | f2.0, 1/20sec

Arches 100% crop (actual pixels captured)
http://img8.imageshack.us/img8/7942/arches100pctcropcenter.jpgFountain 100% crop (actual pixels captured)
http://img94.imageshack.us/img94/9039/fountain100pctcrop.jpgSure there is a different noise reduction algorithm between the two Canons, but default settings for everything on both.
I don't know the technical nuances of the 3MP Pentax Optio camera relative to my 7MP Canon used in the
comparison linked to in the OP, but I see advancement within Canon. The advancements are image stabilization, allowing clearer images. Also newer cameras have improved sensor sensitivity allows for faster exposure to prevent subject blur and user induced image blur. And the sensor advancement also allows less digital noise (grain) in image captures as ISO values increase. Lastly, I'd bet that the DPreview comparison post writer used a tripod for his images, while a sound practice for lens comparisons, who carries a tripod with their compact P&S?