Are you saying you don't think the desktop needs a Free toolkit on which to build?
The community is expected to fill in gaps it feels it needs (e.g. Gtk+3) and take care of packaging (e.g. for major distros).
I guess that makes me a major part of that.
It doesn't work, however, for Netflix. Which is all people care about. When people moan about Moonlight, what they're really saying is "Waaaah waaaah waaaah I can't use a proprietary DRM'd video service that I pay for, because the Moonlight developers have had to do every bit of monkeywork themselves, since the community never thought to pitch in. Waaaaaaaah"
But have you considered Gtk+? It's cross-platform and has great tools in MonoDevelop, working fine on Windows and Mac when you develop on Linux. MonoDevelop 4 shows how good a Gtk+ app can look on non-Linux platforms.
The problem is that it doesn't matter if your app is responsive and lightweight - a parade of morons will still shout from the rooftops about how bloated and slow it is, because they are bound by religion to say so, not by any commitment to facts or reality.