I have an S100 so I can pretty much sum up its pros and cons.
Pros:
Size, it is incredibly small. You can just about carry it anywhere in a pocket.
Battery, it comes with a Li Ion battery which charges rather quickly and lasts about 90 flash pictures.
Photo quality is very good. I have used lesser digital cameras and the S100 looks much better.
LCD screen is very good. Much better than alot of the other digital cameras (Kodak, Fuji) I've used.
Downloading into your PC is very fast via USB port.
Cons:
Cycle time is very slow. I've heard the S100 has a pretty good cycle time but my friend's Fuji is much faster than my Canon.
Flash is very poor. If it is dark and you are taking a picture beyond 6 feet, forget about it. You'll just get darkness.
Limited resolutions.
2X optical zoom is not enough.
Control panel is quirky and not very straightforward.
Limited manual adjustments.
No carrying case.
Overall, I like this camera for what it is, a compact, point and shoot. This camera is not really one for photo enthusiasts. I use it to take pictures of my baby and carry it around all the time when I take him out.