Hi Joshua,
"Some of the other features, like the tree view, feel a bit more gratuitous."
Hah! "Gratuitous" was the word that came to mind for me also regarding the "tree view" feature.
I've definitely drunk the Kool-Aid on Silverlight and RIAs in general, but on the road to the Silverlight millennium there will IMO be many individual feature experiments that quickly have a gratuitous feel.
My first reaction to that one feature was. Wow, that's pretty cool. Then 5 or 10 seconds later it was: "gratuitousness poster-child". By contrast there are other RIA examples (for example the whole Silverlight Airlines sample) that have me saying "wow, that's cool", over and over again, because the Silverlight-ness really adds value.
IMO, another example of gratuitous Silverlight animation that quickly became so annoying that today I blocked its URL with Adblock in Firefox is the "Subscribe to RSS" animation in the Silverlight forums: http://silverlight.net/forums/p/3840/11202.aspx#11202
Alan Cobb
www.alancobb.com