I've released some results of benchmarking of performance with hstore on my blog at http://www.paulnorman.ca/blog/2014/03/osm2pgsql-and-hstore/ The short version of the results is - Use -k (--hstore), don't use --match-only or -j (--hstore-all) - There is very little performance hit for -k - There is more of a size increase