I was a subscriber to Spotify Premium for the past 5 years and loved every moment of my time with them. Their team of music professionals seemed to get all aspects of online, ad-free, subscription service absolutely correct! I was even somewhat of an evangelist for them as others were still beaming about their addiction to Pandora.
However, since I already have an Amazon Prime subscription, I couldn't justify paying another monthly fee for Spotify. I closed my Spotify account knowing my options in available music would change, but it simply came down to savings.
My opinion of Prime Music is in one word - limited. I wasn't expecting 1 million songs to seem so lackluster, but that's what it feels like right now. Hopefully, like their tv/movie streaming it will only get better.