Is Spotify cost prohibitive with Australian mobile data plans though? I know with the amount of music I listen to, my plan would be quickly reached if I swapped to Spotify instead of my local music.

Also, the network availability (especially on train networks) where I'm generally listening to music probably means that my song is going to cut out.

Around the house, Spotify is great (or an alternative like the just launched iTunes Radio) but out and about I still think there's a big market for local music files.