Practically identical to its predecessor, the G11, the few updates to the Canon PowerShot G12 include 720/24p video capture--a much-needed boost over the outdated VGA movies--now with stereo audio and a Mini-HDMI connector. Like the S95, the G12 also adds an HDR scene mode that combines three shots. Unlike implementations that take advantage of fast BSI sensors, however, it requires the steadiness of a tripod, making it only marginally useful.
As you'd expect, the G12's image quality mirrors that of the G11's. It looks great at the lowest ISO sensitivities, with excellent color and exposure; you can start to see a slight bit of detail degradation starting at ISO 200 that becomes more overt (along with noisy) at ISO 400. ISO 800 is probably the highest usable setting under the most forgiving circumstances. Picky shooters really won't want to go beyond ISO 200.
Unlike the LX5, processing the G12's files as raw doesn't deliver an unambiguous advantage over the JPEGs. The artifacts and colors are a bit different, and you might be able to gain a little sharpness from the raw, but it doesn't gain you any shooting exposure advantages.
The G12 lens is quite sharp. Though it's not terrible, the G12 does display visible barrel distortion at its widest of 28mm as well as a bit of fringing on high-contrast edges, especially close the edges of the frame.
Unsurprisingly, the video looks better than the old VGA offering, and overall is pretty good for shooting short clips; it's certainly worth it compared to a typical mini camcorder. Plus, the articulated LCD, stereo mic, and mic jack add to its video flexibility. But it lacks the ability to zoom while recording, and there are no manual exposure controls save exposure compensation and the built-in neutral-density filter.
The G series' unremarkable performance hasn't changed significantly in generations either, and the field in general still lags behind the LX5. It powers on and shoots in about 2.1 seconds. In bright light, shot lag runs 0.4 second, and in dim light that increases to 0.6 second, shaving about 0.1 second off the G11's time. There's a relatively large 2.2-second gap between sequential JPEGs--2.5 seconds for raw--and adding flash recycle increases that to a ho-hum 2.9 seconds. While its continuous-shooting rate bumps up to 2fps from the G11's 1.1fps, that's still slow enough that you really don't want to count on it for burst shots. Especially if you're used to shooting with a dSLR, the G12 doesn't feel very fast. But part of that's perception; it's certainly zippy enough to catch animals a reasonable percent of the time. The articulated LCD remains big, bright, and useful, and in practice the optical viewfinder feels almost identical to the P7000's.