Here's a post about the technology behind SoundCloud from a couple of months ago [1]. I agree that this is a great example of a cloud service. While it might not be completely optimized for one particular platform, I am able to hop between IOS, Android, and PC browsers with all my data being updated flawlessly and in realtime.
My biggest peeve with SoundCloud, though, is keeping track of what I have listened to and trying to remember a song that I thought was amazing. I didn't have an account for the first several months I was using it, but I would just remember the Artists I like and listen to their profiles/likes. Not being able to remember songs and artist names motivated me to make an account and start following them, and liking the songs I wanted to hear again, reblogging the ones I want to share with others... In the end, even though it was frustrating for me, I suppose this is good for SoundCloud and getting people to provide feedback.
[1] https://news.ycombinator.com/item?id=7878433