I really use SoundCloud for discovery purposes, and it's very good... Although the recent changes to mobile have significantly hurt a user's ability to explore on the go.
Generally, I'll explore by finding track that I love and then seeing who has reposted those tracks and then exploring their reposts/likes... rinse and repeat.
Personally, I really wish that I could find people who shared a similar taste in music AND were very likely to repost. Especially now that mobile users are limited to their feed, I want to have more options within my feed to explore, but right now it's very thin.
It's difficult to find those users.