While we're on the subject of Dropbox, Fraser Speirs' timely request for a means of getting an audio file into GarageBand on iPad piqued my interest enough to to a bit of digging around. I've had reasonable results using Dropbox as a way of moving text/image/pdf files around with Apps like GoodReader, so I was keen to see how it works for audio.
Turns out it's doable, in a reasonable but roundabout fashion. Kymatica's AudioShare is a 'document manager' for audio files, handling various transcoding, clipping and copying functions cheaply and easily. It links to Dropbox so you can bring in an audio file, transcodes it to something GarageBand can handle, and moves it to the system clipboard. From there it's simple to paste it into a track in GarageBand on the iPad, ready for overdubbing, processing etc.
There goes another thing that we used to need the desktop computer for.