Mayor and Paul,
My SD850 is very similar to your SD800 and SD890 as they were close to the same generation in features, digital processing software and sensor. So I would expect the results with those cameras would be similar to the SD850 example. You can be happy with your shots as I have until you do a side by side comparison with a better camera. The Canon S95 has a much larger sensor thus potentially better captured photo quality. It also has a faster lens for low-light and probably better (assumed since newer generation) in camera digital processing. Probably the best feature besides the Auto setting mode and the various custom Scene modes on the Canon SD8xx series cameras is that it also has DSLR like capabilities in being able to shoot with Aperture or Shutter speed priority, or even full manual settings. I can also Program my settings so they come up everytime automatically and store them as Custom settings. I’m not sure any other carry in your pocket camera has those features. There are some not so pocketable cameras that do like the Panasonic LX3 and Canon G11.
It also has a couple of features not found on other P&S cameras in that it has a Low-light setting that allows you to shoot in extremely high ISO up to 13,200 and an HDR (High Dynamic Range) shooting mode where the camera takes three bracketed shots to capture and average out the highlights and shadows in one picture.
There’s a lot of stuff to learn how to use for the right photo situation just like a DSLR. My mind was made up when I muffed three straight shots with my SD850 at the Chez Jude restaurant trying to photograph in a low-light situation and the camera would not focus, and the flash burns out most photos when you try to shoot in macro mode. That was the whitefish in parchment where you only got to see it covered only in the paper bag.
What I am missing, but not in restaurants, is DSLR lens flexibility. I would never be able to shoot the moose shot and upcoming bald eagle shot I will be soon posting in the Minnesota North Shore trip report. I shot those with a maxed out 300mm telephoto lens with my DSLR. In side by side testing against my DSLR the S95 is holding its own in photo quality. It was the stealth carrying and low-light without flash capabilities I was seeking.