Folks have started downloading TFS Beta3 and are already reporting success. For instance, read Sam’s account here. And Etienne’s here. We’ll be watching the Team System forums and other blogs for the good word but so far things are looking very promising. Sounds like if you read the fine manual and heed the new System Health Checks, you have a high likelihood of success.
PS: If you have questions about go live, production use of the system, Rick's blog on the topic. He even talks about the question of timing which folks have been asking about.