From what I've read about updates in the LW beta versions, the media player has gone thru some improvements. And apparently they're still working at it bit by bit, or is that now & again, lol well, it'll get better than what it is now in the present official release.
I'd have to agree with Norm about the previewing. It's a pain to have iTunes copy a partial file to its library. I don't believe LW dev's are making a deliberate attempt to copy from another p2p app. Dwnlding music, a player goes with it, a tool of the trade so to speak.