Neil says:

"People are looking for something familiar to compare XAML to, usually comparing it to XUL, since they are both XML languages for constructing user interfaces. They do have very different purposes though. XUL was primarily developed for constructing Mozilla's UI, and for constructing web oriented applications. It wasn't designed so one could write a better alternative to Microsoft Excel or Adobe PhotoShop. Thus, XUL builds on existing web technologies such as CSS and JavaScript. Web developers are familiar with these so the transition is much simpler and smoother. XAML, on the other hand, is a transition only for .NET developers since it contains things from there but contains almost nothing from the Web. The gap is much too large for web developers, which may mean that it may have trouble getting any usage by that group."

I really like the statement "It wasn't designed so one could write a better alternative to Microsoft Excel or Adobe Photoshop". Longhorn is a platform for all applications, and so the pillars - Avalon, Indigo, and WinFS - must support that large of applications being built on top of it. When we designed XAML we wanted to ensure that any scale of application could leverage the power of the platform with a simple declarative markup...

I also agree with Neil that "The gap is much too large for web developers, which may mean that it may have trouble getting any usage by that group"... this is something we are constantly concerned with. We need a platform that scales from VB to C++, from Web to Win32, from applications to documents... whenever you try to address such breadth it is always a concern that you will miss people. We are really trying to make the platform accessible to web developers, we hope to get feedback on how to do that (without making it impossible to also get the Win32/C++ devs also <G>)...