I've had my G9 for about two months, and have used it primarily as a travel camera, most recently on a busuness trip to Belgium and a cross-country road trip with my girlfriend, i.e., occasions when photography was not the primary objective of the trip, and there was a premium on traveling light.
When used within its limits (decent lighting, not too much contrast in the scene), it can produce images that are as good or better than my 20D when printed at 12x18, but there are definitely compromises made. The optical viewfinder is pretty useless, so I've had to adapt to composing on the LCD. But at least it is a large and bright LCD, so it's not as bad as it could be. On the plus side, the controls and menus are well laid out, and similar enough to the 20D that one can transition between the two without much confusion. As nearly every reviewer has pointed out, high ISO images get pretty noisy, but since I work mostly in B&W that noise looks similar to grainy film, and isn't quite as obtrusive as it would be in color. The IS function works really well, so I can hand hold at a lower ISO to minimize the noise issues.
Overall, I like the fact that I can get great images from a camera that fits in my pocket, but I'm always happy to get back to my SLR when size and weight are not a consideration!