Samples photos shot with the Sony Cyber-shot DSC-G3.
Though the G3 technically can shoot as high as ISO 3,200, like many of its competitors its photos become unusably muddy starting at around ISO 800. Up to and including ISO 200 the G3's shots remain relatively sharp and noise-free; at ISO 400, it depends upon scene content and output size. For instance, you really wouldn't want to use it for something with a lot of detail, like this. But as subsequent samples show, it can be acceptable.
You can see the color noise at ISO 400 (left) vs. ISO 80 (right), but at small sizes it doesn't seem to have a detrimental effect on photo quality. (left, ISO 400, 1/10 sec, f3.5; right ISO 80, 1/2 sec, f3.5)