This likely isn't much of a game changer for me. I use Spotify ($10/month) because there is a Spotify app for my Squeezebox Touch, so I can access all of my Spotify playlists from any computer on my network to easily control what music I hear in my bedroom, where I spend most of my time. (I work from home.)
I don't think anybody is doing any development for the Touch anymore (I mean come on, it is FOUR years old for heaven's sake!), so i doubt that I'll get that same functionality with Amazon. (The touch is not listed on their Amazon Apps page, where devices like the Roku and the Sonos players are.)
I heard about this earlier today and installed. I do like it. I don't get any commercials or repeat of the same songs. Looks great and another good benefit to Amazon Prime. Now if only they would let their streaming stuff come to a tablet that isn't a Kindle, I'll be set!