There are a few posts on the pgsql-hackers mailing list that have some more detailed information, for anyone interested in reading more about the approach taken: http://www.postgresql.org/message-id/5CFE0CA1-E5CC-4CD1-9D0B...

I think this is a fascinating approach to improving query speed. It certainly won't be applicable to every use-case, but it seems like there's a lot of value in it.