There ain't none. The ergonomics of the AirStream are the ergonomics of iTunes and, just like Sara Lee, nobody doesn't love iTunes. You play your music just as you would from your desk, and everything works and responds precisely the same—except instead of tinny desktop computer sound you get glorious big audio system sound.
Even better: If you have an iPhone/iPod Touch, you can download Apple's free "Remote" app and your portable now becomes a remote control that replicates your iTunes player right in the palm of your hand (without the cumbrous interface and stately response-times of DLNA-based solutions, whether outboard or built into an A/V receiver). Sit in the sweet spot in your comfy chair and make your selections. Provided that you've ripped your important music in uncompressed or Apple Lossless formats, it doesn't get much better.
Or, more accurately, it can't get much better. Alas, iTunes will not gateway hi-rez audio files of any sort (without the help of a costly software plug-in, that is) so I wasn't able to listen to my growing library of 96/24 music from HDTracks.com and other sources via the AirStream. (Web rumors suggest that Apple might open iTunes to lossless 96/24, including my favored FLAC format, in the not-too-distant future. Here's hoping.)
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