Supercrumbly (can only find their Matrix name) wrote an autorig script.
Olivier Ladeuix did a walk thru tut of how to use it
also someone made an autorig based on Jason Schliefer's animator friendly rigging technique's.
Ladeuix says the abautorigger is all node based, while Schliefer uses set driven keys and expressions which he thinks are slower.
My TD at work agrees that expressions are the slowest, but he says it's old school thinking because computers are so much stronger these days. (though I think Ladeuix has more experience then my TD)