I've been looking all around to find a decent review that shows me how good is the quality of Spotify's "High quality" streaming. No luck, so I'll do one.
CD RIP (flac)
This is the spectrum and wave of the original, 1996 CD version:
320kbps MP3 from CD RIP by ffmpeg
Spotify high quality (desktop) streaming
( Recorded with audio-recorder[^3] into flac. )
Spotify normal quality (desktop) streaming
Conclusions: high quality is still not CD, but is far ahead of the 320k MP3 output of ffmpeg.