I paid for mobile ($12) instead of standard ($5) now that mobile is available to everyone not sure why I am not just paying $5, but they removed that plan now.
Premium allows 320kbps streaming and offline storage.
I had to disable offline storage, spotify maxes out my 50mbps uploads link if i use it (p2p crap), with no option in the app to disable that.
Mobile clients don't do P2P, due to battery and bandwith concerns
The desktop client is what I am talking about, it will try and use as much upload bandwidth as you have if you put popular tracks in offline playlists.
AFAIK, the Spotify desktop app throttles the amount of upload so that it shouldn't disturb the user (or at least, it used to do that). If it used up all my upload bandwidth, I would consider that a bug and file a report.
I did, they dicked me around and suggested to disable offline playlists or reduce my cache size to fix it.