Probably the biggest drawback to Spotify as a heavy user has been the arbitrarily low music library cap the company imposed. 10,000 might seem like a big number in isolation, but when it comes to music, that's not actually a ton of songs. Well, that won't be a problem going forward. In what I will argue is the biggest news of the week, Spotify is getting rid of its ridiculous 10,000 song library limit, and imposing no cap at all.
The error message you would see when your library fills up (as happened to me in January and I'm still salty about it.)
Switching to an unlimited music library is probably the most rational decision Spotify has ever made, given how its recommendation algorithms work. Discovery Weekly doesn't care if it's recommended a specific song to you before, or you've played it a ton of times in the past. Unless you add it to your library or explicitly mark it as something you don't like, it will just surface in a future version of your Discover Weekly playlist again. (Some weeks it feels like nothing in my Discover Weekly is actually new to me.) But with the new unlimited library sizes, you can "like" any song you're even vaguely into and ensure it won't appear in a future music discovery playlist.
I ran up against the library limit in January, and that was after being very careful not to save full albums from artists I liked. Even being so picky wasn't enough to avoid hitting the 10,000 song wall, and I've had to go through my full library more than once picking and choosing songs to remove. Words cannot express how glad I am to hear I won't have to micromanage my music library going forward. It was a lot of work.