I don't know if anyone noticed this, but the video told us that quad cores will work with socket AM2! This text from AMD's site confirms it too:
Additionally, 1P systems using AMD Opteron processor for socket AM2, support unbuffered memory at frequencies up to DDR2-800, which can further benefit application performance. In 2007 the same DDR2-based platforms will be able to upgrade to Quad-Core AMD Opteron processors, without requiring thermal or cooling infrastructure changes, for significantly more performance.
I know that there has been a lot of talk on AM2 and quad core support and a lot of people didn't believe it before this. This should settle that discussion.
Should be fun to drop one of those into my system in about 9 months. May go with a dual-core, though, since quads are bound to be very expensive.