I'm never going to be satisfied with Spotify's recommendations until it's easy for me to curate the input to the recommender.

As things stand, to prevent Spotify from giving me crap recommendations, I have to keep secrets from it! If I want to listen to Led Zeppelin once but don't want Spotify to think "oh I should recommend classic rock from now until the end of time", then I have to go to a different app (YouTube or whatever).

There's a "private session" feature in Spotify which allows me to prevent searches and listens from entering into history, but Spotify really really doesn't want me to use it — it's cumbersome to access and it gets turned off automatically after a few hours.

EDIT:

The satisfaction achieved by whole-account recommendations determined by algorithm described in this post is going to be crushed by some app which gives me a UI where I can say "give me recommendations based on these N arbitrary things". Not just "this one artist" or "everything in my history". Let me design my own recommended channel.