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 folder to your iOS device. It allows you to set up playlists of tunes in your Dropbox, use your earbud controls as if you were listening to iTunes and listen to music in the background while performing other tasks.
And if Music Beta does ever come to iOS devices, Wired author Charlie Sorrel points to a another potential advantage of BoxyTunes. Uploads may be faster as Dropbox creates an MD5 hash of every file you upload and won't upload a second copy if that file already exists on their servers.