It has been in production use in one of our projects - a template-
based code generator. It is closed source, so I can't demonstrate it,
but it has worked reliably for about 6 months now.
It does not use the caching engine, so that has yet to be proven in a
real-world application.
The Smarty-style wrapper has been work in progress for a while, and no
major updates have happened the past couple of months - this is due to
the fact that I am emigrating to the US; I am currently too busy with
paperwork and practical details. Moving from one country to another is
a huge undertaking...
I hope to pick up work on Outline again this fall, after we're settled
in the States :-)