The list of differences between the Canon G12 and the older G11 is a short one, but a crucial change has been made in how the PowerShot G12 records video. Where the Canon G11 offered only an anachronistic 640 x 480 mode, the Canon G12 gets with the times. You get 1,280 x 720p, 24fps recording, which is a significant step up.
It isn't perfect, though. The Canon PowerShot G12's H.264 recording is good, but video enthusiasts will prefer AVCHD, as offered by Panasonic's high-end compacts. There's also no way to access the Canon G12's formidable manual modes, which is frustrating.
You can't even access the optical zoom while recording – presumably on the grounds that the camera would pick up the noise of the motors. On the plus side, the PowerShot G12's optical image stabilisation works fantastically well, even at the lens's full 140mm zoom.