Keep Waiting......
Neither camera has been reviewed yet.
Both cameras are hawking digital stabilization, which is not the same as lens stabilization or sensor stabilization. They classify it as "Anti Shake", not stabilization.
I would wait for a review to find out just how well digital stabilization works.
Also Olympus is claiming ISO 3200 for the Stylus 810.
This is associated with some new technology, that needs to be tested by a reviewer.
Here are the press releases:
http://www.dpreview.com/news/0602/06022106casioexz850.asp
http://www.dpreview.com/news/0601/06012603olympus_810_700.asp
...
..
.
Hi guys, which one do you think is better, casio exilim Z850 or olmpus stylus 810? I've waited for more than 2 weeks, and it's not been updated yet.
I need it for quality picture, Image stabilization and the size!
thank you !!!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic