As promised to the community the Nokia N900 San francisco build has been released. As stated previously with relation to this build it is NOT designed to be a everyday phone, as the name suggests it is a Developer Edition and to be used primarily for that purpose.
Here is a Video of the User Interface in action at the San Francisco conference, also in the video you can see the recently released Tablet UX running on a N900 (what a versatile device).
Another additional video has surfaced by Amanda Lam