Nick "Drudge" Penree writes that he took my tip for boosting audio and made an Installer.app package that does all the work. It's called AudioAmp and is available in Tweaks 1.1.2. TUAW readers have reported various levels of success with the package. Some readers are delighted. Others feel it overboosts the volume.
I finally had my chance to test this hack more impersonally. I grabbed my Radio Shack Sound Level meter, installed the tweak and tested levels during playback. I put the sound meter and the iPhone on a table and kept both units in the same positions through all the tests. I made no change to the volume bar (always set at the maximum), or the music (Beach Boy's, "Sloop John B", always starting playback at the beginning). I remotely rebooted the iPhone after each test via ssh so I wouldn't mess up the positioning on the table.
And my results? Identical readings for sound levels, whether Default > Default was set to 0.99, 0.70, 0.45, or 0.30.