I was happy with mimetic, except it didn't have the facility to decode encoded header-values. I wrote some code, but it was broken, so I made the decision that we should move to something that made this easier, and GMime was chosen.
Jeffrey Stedfast was very helpful in answering my questions with near-perfect code samples.
Beyond that this release features some more Lua primitives and a couple of bug-fixes.
The only annoyance is that the version of GMime I'm using, 2.6.x, isn't available to users of the Squeeze release of Debian GNU/Linux. It is available as a backport, but that means building binaries with sbuild is a pain - due to #700522.
So for the moment I've only built binaries for Wheezy users.
ObQuote: "You know who I am, I've not been off TV for that long!" - Alan Patridge, Alpha Papa