What about mobile versions? Spotify's shady business tactics is why I gravitated towards Rdio and covered the gaps with Grooveshark.
What if you use the web version?
That's one good question, up to this point I've only had the chance to use the main Application. Although, I doubt that they would do P2P from the browser, since they need to have the songs cached in your computer before being able to become part of the P2P network.
That is what I though. I stopped using the desktop version after suffering for highly CPU usage from the client... Also I don't want 10GB on my HD :P