The press release announcing the product makes no mention of whether this chip is a Prescott core, is built on a 90nm fab process, or includes SSE3 support. However, I supsect all three things are true. Intel does say this chip is "drop-in compatible with existing systems," however. We'll see if we can find out more.
Update: We are hearing multiple reports this chip is still a Northwood-derived 130nm design with more square acreage than the Louisiana Purchase. Seems to have a 400MHz front-side bus still, too.