(Yes on the cross-posting.)
Some (most?) of the people espousing web continuations definitely seem
to be trying to do richer more GUI-like web UI, or trying to make the
same code work identically both on the web and on the desktop. So
that does seem to line up with Don's, "probably a bigger win for
desktop GUI apps" thesis.
On the "are the web GUIs your write complex enough to worry about"
question, well, I personally have been spending only small
percentages of my programming time on web work of any sort (much less
complicated web UIs) for a few years now, so I'm clearly the wrong
person to answer that question. But I'm definitely interested in what
others think about it, as in Don's posts above. :)