Thanks for your response. Keep them coming.
What I think would help the most is to display a small box at the top of every page on the beta site that lists all the major problems you've identified that you know have to be fixed before the new site can become the default. Ideally, each one should be a link to a page that explains the problem in more detail. This will help us to understand that you really are listening, and trust you not to plow ahead with something that's obviously currently broken.
The problem isn't that the beta site is broken. The problem is that we don't trust you to fix it, because we don't understand why you broke it in the first place and we're afraid you don't think it's broken. Please, put our fears to rest! :-)