First Whidbey Beta 1 doesn't work with the build available on MSDN. According to the newsgroups, it only works on this magical mystical build 1184 that only official testers have.
Then Yukon Beta 2 only works on a build after the magical 1184 build.
Now this, Win64 for x64 won't see the light of day till sometime next year as a released product. http://www.eweek.com/article2/0,1759,1628259,00.asp
What is someone to do with a AMD64 bit system that won't run Whidbey or Yukon.