I've seen discussions about this feature on other boards and was wondering how people feel about it here. Since I live in a condo and listen almost all the time at lower volumes, I always had the loudness button engaged.
However I experimented recently and instead of using the loudness button, I have left it off and instead moved the bass tone control to about 2 o'clock and the treble tone control to about 1 o'clock. I think it sounds better. Still fills out the bass at low volume levels but not as boomy sounding as the loudness button, so the sound is more open an airy as well.
Listen to it however it sounds best TO YOU. One of my systems sounds better with the loudness button on all the time, so it stays on. The other system, it depends on the volume and recording. It gets used as needed.