I have been playing with osmosis/postGIS this week. I was finally was able to import the MA OSM extract today using osmosis.
It took a lot longer than using osm2pgsql and I was very surprised at how large it got when it was imported.
massachusetts-latest.osm.pbf - 205 Megabytes massachusetts-latest.osm - 5 Gigabytes - 25 time (it is an XML file) PostGIS snapshot db - 10 Gigabytes - ???
It looks like PostGIS/osmosis is not noticing that we repeat the same tags, over and over, and over again in the data.