Hi. When I think about UI framework, I think about Notepad, specifically, what kind of framework would it take to do give any junior dev a task of making a Notepad that looks as simple as Notepad but was actually more like Google Wave/Wikipedia behind the scenes* without it being difficult for the junior dev to do, because the framework/libs would do all the complex things and do them so well that you could write a desktop Wikipedia killer in two weeks.
Since you know about C++, maybe you can tell if there's something like a lib/framework that already solves this problem neatly, or atleast whether you think the features/abstractions/whatever needed to make developing this quickly, easily and correct should be in some framework:
* Imagine a multi-user editor control where many users can edit the same content simultaneously across network so that local memory usage stays fixed to what is visible/audible + some amount forward and backwards in the shared stream - the content could be multi-dimensional (to base a 3D wikipedia, "Third"-Life etc). The content's underlying binary format may vary and should be pluggable, it could be anything, with sub-formats embedded. Ideally you could write the format specification in some sort of specification language and the specification compiler would tell you if there are issues in the specification which prevent the compiled implementation in the destination language from satisfying the requirements I inferred to above.
edit: I just remembed DirectShow. DirectShow Editing Services is perhaps for videos about half of what I think a Notepad vNext needs for some basic functionality.