I'm a NooB, but...
Frankly, anything above the quality of 96kbps Nero6 HE AAC is wasted on me, at least in terms of portable listening, which is about all I do, except for the onboard (SigmaTel) sound chip of my Gateway PC, which doesn't really seem to significantly outperform my Sony DAP.
I tend to fall into the category of hearing ability represented by the test method at Audio quality of aac vs. mp3 vs. wma vs. ogg encoders - SoundExpert
. It's really a nice place to help people find a good format and bitrate for portables.
In fact, I would say the transparency level is somewhere from 4.5 to 5 on their scale, for me.
I'll have to look into it again when I get some better equipment.
I'm accepting donations