Menu toggles in the new "Menu" interface (Pages, Categories, etc -- on the left) should match the existing slide toggle for individual menu items. It's an abrupt show/hide and doesn't match the UE expected in that area.
Also - shouldn't the arrows on the left change from being pointed down to pointing up when a toggle section is open? Clear for most, but again, about consistency.
Hover state of sections on left don't match existing WordPress UI elements either. On hover, it's a slightly darker gray and then when active, becomes the dark gray (as the main menu system does on the left) -- new "Menu" UI doesn't match this.