As no one responded, I guess I am the only one who has experience so far with the G1? I purchased it last week for $629. Retail, didn't see worth it, but at that price it did. So far, no complaints. Seems to live up to the mostly positive reviews. Easy to use, works as advertised, pics look great, but have not had time to take any pics of note for real comparisons and I am still getting used to digital as a medium beyond simple point and shoot cams.
It's hard for me to view this cam as more then a toy. I am still locked into cameras as being larger and heavier as "real" cameras. My Nikon f100 for example is built like a tank.
It seems camera bodies in general are lighter these days until you get up D300 or so, at least in the Nikon line.
Having said the above, I'm still tempted to get an N90 instead, but the size and weight of the G1 is impressive for what seems just slightly less quality and less ISO flexibility.