In fact, it's probably not entirely fair to compare the SX100 IS with the TZ3 or R7, because it really doesn't resemble either camera that closely. For a start both of those cameras have fairly sleek, compact metal bodies, while the SX100 IS is made of plastic and is quite a chunky little thing, measuring 108.7 x 71.4 x 46.7 mm and weighing a not inconsiderable 266g empty, or around 316g including the pair of AA batteries that it runs on. This for me is something of a problem, because the camera is designed as a compact, with a single wrist strap. The Fuji S5800 is slightly larger and about the same weight, but has a neck strap and more SLR-like handling. The SX100 IS is too large to fit comfortably in anything but a large pocket, and too heavy to have dangling from your wrist. The Panasonic TZ3 by comparison is 105 x 59.2 x 36.7 mm and 257g loaded, and the Ricoh R7 is only 99.6 x 55 x 23.3mm and 135g. There is a soft case available which may have a belt loop or neck strap, but it's an optional extra.
Of course being a Canon the SX100 IS has superb build quality, and the plastic body feels very solid, with no flexing or creaks even when squeezed. The body has a very rounded shape, with all the corners and controls smoothed off leaving no protruding edges. The relatively large size does mean that there's plenty to hold onto, and the handgrip, while smooth and untextured, is large enough to be comfortable, and there is plenty of room on the back for your thumb, so it provides a secure grip.
The control layout is fairly straightforward. The top plate bears the main mode dial, with a clearly-marked Auto setting, four simple scene programs (portrait, landscape, night snapshot, kids & pets), a scene mode setting with a further seven scene programs, and a full set of manual exposure options. On the back is a large rotary thumbwheel/D-pad, a feature Canon has used on a number of its cameras, often to mixed reactions from users. Some find it impossible to use, while others find it very quick and intuitive. Here its rotary action is used to select scene mode options, enter exposure values in manual mode, and control manual focusing, something for which it is extremely well suited.
The other controls are a row of buttons below the monitor and the usual array of secondary functions on the D-pad, including focusing mode (normal, macro or manual), ISO setting, drive mode and self timer, and flash mode, although this is only available when the manually-operated flash has been raised. I would have expected that in automatic mode the flash would have popped up by itself, as it does on several other cameras, but instead it merely prompts you to raise the flash with an on-screen warning when shooting in low light.
There is also the usual Canon function button, bringing up an on-screen shooting menu for image size and quality, a versatile array of colour modes, manual flash output adjustment and metering mode. The monitor itself is clear and bright, and has a glare-reducing coating. At 2.5 inches it is a good size, but at 172k pixels it isn't as sharp as some. For manual focusing a magnified area appears in the middle of the screen, and a two-stage range control makes close-range focusing very accurate, but at longer ranges it is a bit hit-or-miss.