I do agree with you the new full screen ui is about annoying to use but I think there should be an option to switch between as I actually like the look of the new UI although the pop down thing isn't a good thing. Aswell as how come it only pops up for some songs now?
I personally hate the new UI and hope it never becomes available unless there is an option to enable/disable it. I don't even listen to Spotify's playlists (like Mint, etc) anymore because of the stupid UI. If they force it on my own playlists, I would probably cancel my membership. It has been months now that Spotify has been fooling around with this and I wish they would just make up their mind and do something with it rather then being inconsistent. There was a press release a few weeks ago that showed some enhancements, but personally haven't seen them in any playlists on my account so I can't tell if its any better or not.