A few days earlier than originally announced, the list of backwards compatible titles on the EU PS3 has now been released. The Sony site details games on a three tier basis, giving results for titles that have no known issues, some minor issues, and noticeable issues.
Unfortunately, that is as detailed as it gets at the moment. I jumped straight to P to check out the Pro Evolution Soccer results and it isn't looking good, although of course this is work in progress. God of War 1 and 2 are fully compatible, as is Final Fantasy XII.
While the list isn't complete, and it seems a mixed bag when it comes to compatibility, it's safe to say the PS3 beats the 360 hands down on compatible titles, but with no next-gen Pro Evolution Soccer and no fully compatible current PS2 titles it seems a bitter pill to swallow.