The Canon PowerShot S95 is a very good, popular camera with some commonly complained-about flaws: among those are the poor flash design, lack of a grip, narrow maximum aperture at the telephoto end of the zoom range, short battery life, slow performance, and relatively expensive price. With the S100, Canon addresses a few of these plus it adds some desirable new features: a wider-angle 24mm start to the zoom range, manual controls and zooming during video, and a built-in GPS. There's also a spiffy new silvery/champagney-color version in addition to the basic matte black.
Despite a slight bump up in resolution, the S100 maintains the excellent photo quality that contributed to the S95's popularity. Exposure and metering, color accuracy, and tonal range are good, and the lens is relatively sharp; there's some distortion but less than you'd expect given its minimum focal length of 24mm-equivalent. Given its size (and its relatively small sensor) it delivers excellent JPEG quality up to ISO 200, and photos remain quite good up through ISO 800. If you shoot raw you can even get quite usable quality out of ISO 1600, which is rare for a camera its size. Plus, there's quite a bit of fringing on high-contrast edges. The camera defringes the JPEGs, but if you shoot raw it's quite a bit of work to fix.
High ISO sensitivity performance is especially important for the S100, because the aperture narrows so quickly as you zoom through even its limited 5x range that you run out of available light fast. Shooting in late-afternoon November light became an exercise in frustration. Any zoom beyond its widest required boosting the sensitivity setting. The only thing that keeps me from dinging the S100 harder for it is that bumping up to a faster lens in the Fujifilm FinePix X10 adds a significant chunk of change, and as I haven't tested it yet there's always the possibility that the X10's photos won't be up to its price, or that it somehow manages to perform even more slowly than this generally slow class of cameras.
The S100 does a pretty nice job shooting video as well, and one of the enhancements over the S95 is the ability to use the zoom during shooting, which it does quietly and unobtrusively. The video is sharp if somewhat oversaturated (you can set it to a neutral color setting if that bothers you), and the audio sounds good. There's a slow-motion recording mode--you capture normally and it plays back at 240 or 120fps and saves out an MP4 file of the slow motion playback. It's better than some because it doesn't limit the capture time, but it also records at small 320x240- or 640x480-pixel sizes depending upon the frame rate.
Disappointingly, Canon didn't improve the S100's performance over the S95; it's still a bit slow overall and can't keep up with class performance leaders like the XZ-1 or the LX5. It powers on, focuses, and shoots in just under 1.6 seconds, which is reasonable. For single shots, it's about the same as the rest of the field: 0.4 second to focus and shoot in good light and 0.6 second in dim. But like the S95 it slows down notably when snapping two sequential shots, to 2.4 seconds for JPEG, 2.6 seconds for raw and 2.8 seconds for flash. While I wouldn't call raw+JPEG shooting glacial, it does feel sluggish. It can burst JPEG at about 2.4 frames per second, but as with its peers, you don't really want to buy this model for anything that moves quickly, including kids and pets. It also has the shortest battery life in its class, but that's one of the trade-offs you make for size: smaller camera, smaller battery.
It uses the same LCD as the S95, and it's bright and saturated and pretty usable in direct sunlight.
The S100's design improves on some of the flaws of the S95. It now has a tiny grip in front and a rubberized thumb rest in the back which makes it much easier to hold and shoot. It retains the control ring around the lens that distinguishes the camera from competitors, except for the XZ-1, which copied it. The ring can be set to control shutter speed, ISO sensitivity, exposure compensation, manual focus, white balance, stepped zoom, i-Contrast, aspect ratio, or its function when in Custom mode. The functions can be set independently of shooting mode, so that, for example, it can control focus in Manual mode or shutter speed while in aperture-priority mode. The stepped zoom can also be a surprisingly useful feature for some; it jumps to popular preset focal lengths (24mm, 28mm, 35mm, 50mm, 85mm, 120mm), which is quite convenient if you need repeatable shots. You can quickly access the ring control assignments via a dedicated button on the back of the camera. If you don't plan to change the ring function that often, you can even reassign the button to a host of other options, including some important ones like metering, raw+JPEG override or the built-in neutral density filter.