The news from MIX07 this week has been very interesting.  After watching some of the breakout sessions I thought I would answer Nick Kramer and provide some feedback as to which controls and functionality to include in the final Silverlight 1.1 release.  The decision here is between supporting something at the core level, supporting it as a standard additional DLL or leaving it to the community.  Of course, the more interop between WPF and Silverlight the better, but the size of the download needs to be kept in mind. 

So, in general, my inclination would be to use the following as guidance:

• Include as much of the plumbing as possible.  Adding alternative, competing plumbing solutions on top of Silvlight could drift the design direction away from the solutions used in WPF.
• Ship the controls as an additional DLL.  When I say controls I mean button, textbox, listbox, combo etc..  These file sizes should be very small if the infrastructure is shipped in the core product.
• Work out a way of caching signed DLLs for reuse by other apps.  The assembly resolver should be able to check an assembly cache for already loaded assemblies.  Nothing as fancy as the GAC, just a dynamic cache of loaded assemblies on a best efforts basis.

So, specfically - taking the above....

• Include in the core the infrastructure for ItemsControl, including the virtualization of elements, Panel templates etc.
• Include DataBinding, Styling and TemplateBinding.  A must have for the MVC pattern to work in WPF and Siliverlight.
• Include basic Panel support, additional Panels could be added from other DLLs (imported with ListBoxes etc).
• Include the basic controls where the data that they model is unique - not the behavior.  So, an ItemsControl should be included but the ListBox, ComboBox and even ListView can be included as a sample or left to the community.  Abstract controls providing the base classes are more important than covering the basic traditional Windows controls.

I would also suggest including a new version of the assembly linker that works to intelligently link referenced assemblies together and removed unused functions.  Without this I think the third party control support is going to be limited to source code distribution only.  Who will want to include a 10MB Grid Control if you are only using 10% of the functionality?