I don't like any theater modes and they reduce usability, but I do like the floating panels. The current lyrics and artist bios only show up in panels which you have to go into a menu to enable/disable (Maybe make that just a right click enable left/right panel?) It also forces the spectrum visualizer to lose a lot of resolution and minimize into one of the side panels. Oh, and it also removes the "dynamic" background colors, which isn't very represented with my chosen album cover in the images.
My idea for a new one with floating panels would leave the spectrum visualizer alone and keep the dynamic background color. The spectrum visualizer already changes colors dynamically with each album cover as well, so the text for lyrics and bio could follow that same color scheme. The floating panels themselves in my picture are just a low opacity black to dim the background a bit. I suppose you could potentially add in some options to change opacity and colors there as well.