I'm quite curious to see what they intend to do with this music streaming app, as most people already have a Spotify account? However, as Spotify has lost a bit of its edge in later days (due to a lack of word of mouth), perhaps Twitter will take over as the main streaming destination.
I still think that people will be downloading music but I have a strong feeling that the illegal downloading will increase (especially if we're now also getting streaming apps. I don't see why people would feel like paying for their music- apart from supporting the artists), while legal downloading (iTunes etc.) will soon lose out.
Streaming services are always useful, and with the Underground in London now getting its own WiFi system, it seems we will be able to get coverage EVERYWHERE (not to say London is the centre of the universe...maybe, to me) but I would still prefer to have the downloads there to be used at any time, place or way. A streaming service just seems a bit...risky.