What is the unit of componentization in XAML? Can vendors still create grids, rich-text editors, and such that can easily be "dropped in"? ...or do you need to copy chunks of XAML code and backing code?
XAML isn't like HTML. It only describes the markup syntax - it does not describe the object model. Instead, you can supply whatever object model you like. The examples Chris gives are obviously from the Avalon object model.
So adding a third-party control is pretty simple - you add a reference to the DLL that control is supplied in, then bind to those objects in your XAML markup.
Where can I find a specifications document on XAML?
Is it correct that XAML will only be available for Window forms and not for Web forms?