This looks great! Any plans to port this to Windows?

I am not a massive fan of the background colour of the landing page, it makes the text slightly hard to read. The rest of the page design looks good though.

> any device that supports a web browser, no dedicated client software needed!

The demo seems to be down at the moment so I can't see, why would you need to download anything if that is the case?

(Shameless plug: I made http://playlistful.com/about which is similar to this, but you can't listen to the music on more than device at the same time. That's a feature I really want to add, but I can't get my head around keeping the songs in sync.)