Like the SD790 IS and SD1100 IS, some aspects of the SD770 IS' performance are excellent, while others are below par. It wakes up and shoots in a fairly average 1 second, and delivers great focus-and-shoot times of 0.4 second and 0.6 second, in optimal and suboptimal lighting, respectively. But two consecutive shots take 2.5 seconds and adding flash bumps that up to 3.7 seconds, both of which fall behind much of the competition. The same goes for its sluggish 0.9 frame per second typical burst-shooting rate. Canon rates the battery at 300 shots (using CIPA-standard methodology), which is relatively good for an ultracompact. The 2.5-inch LCD remains usable in bright sunlight, which is good; I found the optical viewfinder too small and distorted to really be an acceptable substitute. It has a nice, wide viewing angle for impromptu slide shows, though it's a bit small for that purpose. Like the SD1100's, it's a fingerprint magnet.
For a sub-$200 camera, the SD770 produces very nice photos. By the numbers, the SD770's photos are sharper than the SD1100's; since they use the same lens, the difference is attributable to the different sensors and perhaps some processing tweaks. The SD770's exposures are a bit brighter and white balance a tad more accurate, which helps improve the perceived sharpness. However, I still found the SD770's pictures a bit softer than I like in all but the dead center of the focus area. Otherwise, its photos have pleasing, saturated colors and good exposure.
For movie capture, the SD770 is pretty typical. It delivers decent quality 30fps VGA with passable audio, but no optical zoom during shooting.
All told, the Canon PowerShot SD770 IS is very good for a borderline budget ultracompact, but you also might want to consider spending a few extra bucks for the better photo quality of the SD790 IS.
(Shorter bars indicate better performance)
(Longer bars indicate better performance)