Mark - I think of the earlier loudness capabilities as a one-size fits all bump of certain frequencies. It adds that bump no matter how loudly you listen, which works much better at some levels than others.
What Audyssey did is came up with a more advanced formula to apply the "loudness" effect. It takes into account all of the Audyssey readings done in your room and then applies their algorithm to bump the right frequencies the right amount at the current volume level. This is different for each room and at each volume level, so it's something that would be impossible to do without linking it to the Audyssey calibration.
Would I like it to be included for free? "Hell ya," but given that it was something new and not common to other receivers (yet), I was more willing to pay for the upgrade. Now that I have, I'm very happy I did. The difference is very apparent, especially when I thought it would be hard to make my previous system sound much better. This is like a whole new level of goodness (the opposite of suckage) that I hadn't imagined possible out of the same system.
Jason
