I have Spotify Premium, and I'm very happy with the sound quality. I have downloaded some songs from HD Tracks, and there is a difference between the HD Tracks songs and the sound quality on Spotify, the HD Tracks stuff that I downloaded sounds amazing. But judging Spotify on its own, I think it sounds great.
When I first got Spotify I did a rather unscientific comparison...ran the USB from my computer into my Peachtree integrated (it has a Sabre 9018 DAC), and connected an Onkyo universal player using Coax into the Peachtree's dac as well, so the DAC was doing all the work albeit from different connections (computer through USB vs. CD player through coax). I then queued up a song on Spotify, and the exact same song on CD, and started them at the exact same time so that all I had to do was change the input on the Peachtree to go back and forth and hear the exact same song, in the exact same place, from Spotify to CD. There was a difference, but to my ears, in my room, it wasn't big enough to override the convenience of Spotify. If I was doing critical listening of a piece of music, I'd listen on CD, but the convenience, library, and quick easy access to music on Spotify far outweighed any difference in sound quality between the two. Spotify has spoiled me...the ability to quickly shift gears from one artist to another, one song to another, at the click of the mouse, much more fun than having to get up, change CDs, deal with handling discs and CD cases everywhere.
Hope this helps...
When I first got Spotify I did a rather unscientific comparison...ran the USB from my computer into my Peachtree integrated (it has a Sabre 9018 DAC), and connected an Onkyo universal player using Coax into the Peachtree's dac as well, so the DAC was doing all the work albeit from different connections (computer through USB vs. CD player through coax). I then queued up a song on Spotify, and the exact same song on CD, and started them at the exact same time so that all I had to do was change the input on the Peachtree to go back and forth and hear the exact same song, in the exact same place, from Spotify to CD. There was a difference, but to my ears, in my room, it wasn't big enough to override the convenience of Spotify. If I was doing critical listening of a piece of music, I'd listen on CD, but the convenience, library, and quick easy access to music on Spotify far outweighed any difference in sound quality between the two. Spotify has spoiled me...the ability to quickly shift gears from one artist to another, one song to another, at the click of the mouse, much more fun than having to get up, change CDs, deal with handling discs and CD cases everywhere.
Hope this helps...