Hi!
I see that the pixel size preview box in the top-right is active, with the possibility of entering units manually. If I do that, nothing happens.
Also, Full screen preview (CTRL+SHIFT+A) is not hiding it. (Also the ruler is not getting hidden, which it should be).
Also, there is no obvious and quick way to hide the box, making it in the way of the working area which can be a problem if anything is placed at that position.
The same problem is with the ruler: it is not needed all the time, yet it stays there, taking up precious pixels and visually “mixing” with the design.
Also, in the preview mode, we don’t get the responsive toggles anymore, and dragging isn’t working all the way, but only to the limit of the currently chosen breakpoint. I think the Toggles should be visible in the preview mode. At the side is OK, as long as we have the freedom to preview the design as we like. 
Personally, In the Preview mode, I’d like to be able to show/hide the ruler and the pixel box and have visible (blue?) lines on the ruler representing each breakpoint. Then it would be great to be able to drag the preview entire way, with possible slight snapping to breakpoint lines.
