The change in style makes it more difficult to see properties. I circled two example areas. In the old version, I can clearly see what is selected by the darkened button. In the second, the dropdown at a glance looks the same no matter which option is selected.
Looking at it further, I think one of the biggest difficulties with the new design is the misuse of contrast. In the first, dark denotes a selection and everything else is 50% grey. In the new design, there is no change in contrast for selected options, and the alternating contrast throughout makes it difficult to read (design should convey meaning, and it no longer does in the new design).
I guess I’m having trouble understanding why something that wasn’t broken is being “fixed”.
edit Maybe part of it is that the combined panels were taller before, and now the dark headings (Layout, Position) etc., really break it up, and are the same color as editable fields.