I'm very excited at the potential of the browser chrome being implemented entirely via standard web technologies. And given that Servo is never going to implement XUL, it would save a lot of effort that would otherwise be spent implementing a bespoke, minimally-functional UI (which has been tentatively named Crow, if the MST3K reference wasn't already obvious).

See also this other thread linked from the discussion in the OP, "Moratorium on new XUL features": https://lists.mozilla.org/pipermail/dev-platform/2014-Octobe...