I'm new to Spotify. I upgraded to Premium with the understanding that files would be stored locally on my computer. The reason for this is that I use an mp3 player not generally supported by any sort of iTunes/Spotify interface (it's a waterproof, bone conduction mp3 player for swimming laps). The only way to get music on the mp3 player is to drag and drop, as if it were an USB key. Is this not possible with Spotify?
Spotify relies on a mostly closed system for streaming and storing tracks, so that artists and labels can be paid for each listen. This unfortunately means you can use Spotify tracks on any device or platform that does not have a Spotify application.