The S100's matte black finish gives it an almost military feel, like it was a stealth camera straight from a covert ops unit. We like the understated design which definitely won't stand out in a crowd. You might want to know though that dust has a habit of sticking to the body for some reason - probably due to the S100's finish.
Almost everything we didn't like about the S95's handling has been addressed in the S100. The S95's flat front was too smooth to hold, and it removed the thumb grip found on the S90. A new front grip has been added to the S100, and a (better-designed) thumb grip is back, both make the S100 easier to hold on to. But the front grip, while improving the S100's function, is unattractively shaped, and we wished Canon had taken a cue from competitor Panasonic's LX5 curvier grip, or Richard Franiec's beautiful custom grip for the S95.
The stub of a zoom toggle on the S95, which always felt like it might snap off, has been changed – now the zoom toggle looks thicker and feels sturdier. The Mode dial is a lot smoother than it used to be on the S95.
The Ring Func. button has been moved from the top plate to the back of the camera, and it can be used to change which settings the control ring is changing, e.g. from aperture to ISO. The button is also a customizable button which can be changed to trigger any of twenty commands. The Func. Set button in the middle of the d-pad brings up a list of common settings via an overlay menu on the screen, very handy for switching things quickly.
What makes the S-series so special are the control ring around the lens and the control wheel on the back. Both combine to give you quick manual control over the camera, something you won't usually find on a digital compact. For example, in Manual mode the control ring dictates aperture settings, while the wheel determines shutter speed. In Aperture Priority mode, the ring determines aperture settings, while wheel sets exposure compensation; but only after pressing up on the d-pad.
The S100's handling is almost perfect but there are little oddities and quirks. For one, you can't completely toggle off all display info on the monitor, there'll always be little numbers obscuring the view. You also can't choose a 'normal' multi-area AF frame, except by choosing Face AiAF, then switching off Servo AF in the menu.
The S100's battery life is short, rated around 200 shots by CIPA on a single full charge (we managed about 230 shots before the camera gave out). If you're buying this camera, either charge it daily or buy a spare battery. Here's a quick comparison of battery life between Canon cameras and the S100 against other manufacturers' cameras, as rated by CIPA (Camera & Imaging Products Association). Like the S95, the S100 has a wild habit of displaying incorrect battery info, you can have one bar left, then power off and on, be faced with a full charge, which drastically drops to a red flashing icon within a couple of minutes.