From an article in Rolling Stone on Apple’s newish (it’s been around since February, but hasn’t been heavily publicized) file format:
Engineers also lower sound input levels as they create the digital files, and use software such as afconvert and afclip to reduce “clipping,” which makes digital recordings sound grungy.
Loudness is the curse of the modern record industry. Just by getting rid of that they’ll improve the quality of digital sound by about 150%. The nice thing is that, unlike label released FLAC downloads, these don’t cost anymore than standard AAC files. And even on earbuds, they sound a hell of a lot better. Not Neil Young quality, you understand, but these things take time.