I would say it's pretty good, I'm not exactly a hardcore audiophile, but no complaints. It is limited to 320kbps since Spotify doesn't allow unauthorised third party clients to stream lossless.

This is the client I'm using - https://github.com/devgianlu/go-librespot

Takes 2 seconds to install it via brew or clone the repo and run it, so if you're curious about it, it's worth a test.