I’ve nothing to say on this one because I’ve just read a great article on it so I’ll link to it;
The one thing I would say is that if I read this correctly it won’t allow for binding via IDynamicMetaObjectProvider and that’s a shame because COM programmability in Silverlight is via late-binding and dynamic objects and so it’s a natural thing to want to do to bind to those objects and it looks like this support doesn’t help in that area.
Where it should help though is in binding to (e.g.) XML which is a topic I’ve looked at in the past, perhaps it’s time to revisit that in the light of Silverlight 5.