I just answered your other question, so I won't say much here. The 12MP point and shoot that I have in those comparisons has the same sensor size as the G10 and the image quality is similar.
If you want to enlarge your pictures to anything more than 11x14 without very much cropping, you will notice a difference in image quality. If you will limit yourself to 11x14 (maybe 16x20) and if you use pretty much the whole image (minimal cropping), you will be okay with the G10 and it will cost a lot less money than a 450D with 2-3 lenses.
