Why are continuations cool?  What new features do they allow?

<ul>
<li><a href="http://chneukirchen.org/blog/archive/2005/03/restartable-exceptions.html">restartable exceptions</a>
<li><a href="http://communicator.sourceforge.net/sites/MITRE/distributions/GalaxyCommunicator/docs/manual/advanced/synch_vs_asynch.html">resolving synchronous/asynchronous mismatches</a>
</ul>