good to see this subject really getting about the web. i was one of the many many that originally thought volume=loudness. how wrong was i.
listening to a well mastered track with dynamics intact and some headroom is a whole differant world to listening to some loud smashed crap.
even when doing home mastering (on my own tracks to play out) im much more aware of getting the loudness thru good use of a compressor and a well represented frequency range.
get it right in the mix and the amount of limiting needed is negligable.