[postgis-users] Geography type: centroids and distance?

[fork]

I have successfully loaded all the PUMA geographies in the US, and would like to
calculate their distance matrix.  Since st_distance on a polygon of these sizes
is sort of a nightmare, I thought I would calculate the centroid and then get
the distances between those.  However, st_centroid(geography, geography) is not
available....  

So, is there a better way?  Should I reproject to 4326 and use
st_distance_sphere?  Or ???

Thanks to all the folks that have made such a cool thing as PostGIS happen!