I found out that Spotify library is very poor. There's lot's of good artists missing - I'm not talking about this new artists like Wiz Kahlifa and all that junk. From Reggae, through Punk, Trip Hop, Hip-Hop, Drum and bass, Funk, Soul, Blues, Rock and not only, I find that Last FM is better! Plus, I can just use it in my browser.
I'm not sure if this is only for paying customers but Spotify does have webui too (https://play.spotify.com/).