Well compared to Canon G2, I would much rather prefer Canon S30/S40. It has the same technology but smaller in size.
I am an owner of Canon S30 myself and I have recommended this camera to lots of people and everyone seems to be happy with the camera.
I have a friend with Sony DS85. I think the only good thing about that camera is that it can take continuous video, whereas the canon s30/g2 can only take up to 2 minutes of continuous shot. The bad thing is that it uses non-standard sony memory stick (could be good if you're a sony-equipped person

)
No experience with olympus.
Go to
http://www.dpreview.com and look at the review of these cameras. Go to the forum as well and ask around.
Good luck with your camera hunt
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