This is cool! Wouldn't it be great to have an Avalon design tool that runs within Visual Studio 2005? Unless you love hand-editing XAML files (and I do, but only up to a certain size), you should try MOBIFORM's updated version of Aurora. This release runs on our Avalon Beta 1 RC. Here's a list of some updated and/or new features from today's announcement:
You can grab the download here.