There's another thing I wanted to talk about but which really deserves its own blog post: the relationship between XUL, the Web, and free desktops.
First, I think XUL and the Web are both great for free desktops. They attack the "applications barrier to entry" that has made Windows too strong for too long.
Second, XUL does not compete with free desktops. For one thing it's very much open source, and furthermore, it's a toolkit and sits above GNOME etc.
Third, the distinction between XUL and the Web will erode over time, in the sense that the features you need XUL for today will eventually be offered as regular Web standards (CSS box model, enhanced widgets, offline execution, WHATWG APIs, etc).
Therefore the interesting question is not "how do we best integrate Firefox with GNOME?", but "how do we best integrate GMail (etc) with GNOME?" We've got some ideas but there's a lot more that could be done.