Ignoring the creative and social aspects and focusing on the parts that I dig... technologically speaking, the site is hella cool. There's multiple ways to get your voice into your audioblog. If you've got a mic and a flash-enabled browser, you can use their site to record the audio directly. You can upload your own audio files (mp3 or wav), if you like doing it the manual way. Or, and this is the really nifty bit (IMO), you can call in from your phone. All you need is a cell and something to say, and you got yourself a moblog.
Anyway, go check it out.