There's a short but interesting analysis on Wired's Gadgetlab about Google's Music Beta service and how a simple US$2 app, BoxyTunes, does everything you hoped Google's service would do but doesn't.
Music Beta was launched last week at Google's I/O Developer conference. It currently only works in web browsers and on Android devices. The web-based service does not work on iOS devices because it uses Flash.
BoxyTunes, on the other hand, simply streams any music, podcasts or audiobooks it finds in your Dropbox
