After an upgrade to Fedora 17, I now have xulrunner-13, and conkeror up-to-date as of 2012-06-19.  The
meta key works elsewhere, but is seemingly completely undetected in conkeror.

[20:51:15][hgb@morag:~]3 xulrunner --version
Mozilla XULRunner 13.0 - 20120605112244