Their recommendation engine is really bad IMO. I was hoping for a futuristic machine learning + listening based recommendation engine that could find similar songs based on what they actually sound like. Mostly they just find songs based on what other playlists your song exists in. It's really boring and not good at finding new music for me. It does OKAY and it isn't why I use Spotify, but I can't help but feel like they are missing the boat here. I remember working with Gracenote software like 15 years ago and it could fingerprint songs and find similar music at least that long ago.

e: my overall sentiment on Spotify is very positive, I just wish recommendations were better.