Totally agree that delivery is a commodity. However, as a user, I ditched all services in favor of Soundcloud because of the discovery part. For example, Diplo and Tiesto post and repost almost weekly, combined with the rest of people I follow you get a stream of the very latest music of your taste, manually curated (reposted) by the top DJ's themselves. It's not just an "upload feature", its like Facebook for music: you hit play and get a tailored endless stream of awesomeness, 0 effort on your part. No need to hunt for and buy tracks one by one. No need to suffer through some unknown Pandora voodoo that turns up the same tracks of unknown recency, over and over. Just follow the people you like, and it will play the latest music you like, simple as that.

I don't know if Soundcloud can manage to build a viable business, sometimes they make changes that piss off users and uploaders, and the current model doesn't look too lucrative. But for me as a user, the experience is night and day compared to the true commodity services (iTunes, Amazon, Google, Pandora, Spotify, etc etc), who I think will soon start to crack under margin pressure like Rdio, Mog and others.