No Build 7000 is not the official beta, I suggest you install B7000 for now and when the beta comes out you can just upgrade, B7000 is very stable, I ditched XP Sp3 for 7 lol
Do you have now proof its not ? Both Ed Bott and Paul Thurrott have confirmed that Build 7000 is the Windows7 Beta.
Build 7000 is the beta build. When the public beta is released, I'm using the keys to activate, validate, and appropriate my Ultimate and Home Premium installs. I will then be able to use them until July and be happy, joyous and free. This is my story, and I'm sticking to it.