Agree completely. Rdio did a much better job with music discovery, but they were limited by selection. Soundcloud doesn't have typical discovery features, but the ones they do have are quite good. Here's how I find good (relatively unknown/esoteric) music there:

- Follow good aggregator accounts. These repost new music regularly, which appears in one's timeline.

- Follow good regular accounts and play their "likes."

- Go to a song's "related tracks" screen and play those

I find excellent music on a regular basis this way.