I wish WAU had a 'beta' pane that showed beta versions of current addons you have installed, so we could help (by being a beta tester) if we wanted, but it would be a choice to load em up. And be able to 'fall back' to a stable (and predictibly working) version if we wished.
This would prbably involve some behind the scenes management of versions and SVN definitions, but is should be doable. And it would save a lot of anguish on the part of the casual users who use WAU and often get unstable updates (betas) of addons downloaded. (see toadkiller's offical Autobar thread http://www.wowace.com/forums/index.php?topic=9138.0 for an example...)
I personally like the idea of having a "stable site" stable.wowace.com, and a beta site beta.wowace.com.