I've only been playing with Volumio for a week at the moment - my current audio setup uses another product. But the first thing that struck me was the elegance and ease of use of the UI. I agree with MattLum - I don't see the advantage of the experimental UI, and it looks cluttered with no real advantages in functionality. I have Volumio 2.692 installed on a Pi Zero W, and it's pretty much fantastic in so many ways - congratulations to the developers.
Could we have the left hand side menu slide in on a click on a tab ... that would free up some clutter (as reported by some earlier users). I quite like the new look, but the really annoying thing is that I can no longer change volume by clicking on the big right hand top circular dial (I try and do this all the time despite using UI 3 for some time). There is a good argument for swapping the roles of these two screen items (control back to the big circle, and volume notification down to the bottom, and do we even need both?). Aesthetically, the simpler, the better in my view, but still being able to tunnel into settings etc. very easily via tabs is good.
Edit: I'm looking at the UI now, and both left and bottom bars look as though they should just be able to slide away to a tab.