You should also read this review on the G11, the follow-on to the G10. Both cameras can perform well in the point&shoot or compact realm, but cannot compete very well with large image sensor cameras with good lenses.
I have a G9 and G11. The G9 and G10 produce noisier images as you increase the ISO, while the G11 and G12 produce somewhat less noise at higher ISOs. They still are not great as the ISO climbs. There is a comparison shot at the bottom of the above review between a G11 and a GF1. Quite a difference. The G9 and G10 do their best at ISO 80, as you raise the ISO their images show degradation.